[Recent advances in pyridoxal phosphate-dependent enzymes and their applications].

Pyridoxal phosphate (PLP), the active form of vitamin B6, is an important coenzyme in various enzyme-catalyzed reactions. PLP-dependent enzymes can catalyze a variety of chemical reactions, such as racemization, decarboxylation, ß-addition, ß-elimination, retro-aldol cleavage, transamination, and α-elimination. They are biologically synthesized a powerful tool for a variety of natural amino acids, non-natural amino acids and their related compounds. This article details the structural features and catalytic mechanisms of typical PLP-dependent enzymes such as ω-transaminase, lysine decarboxylase, threonine aldolase, and L-tyrosine phenol-lyase, and reviews the research progress in molecular modification and industrial applications of these enzymes. Finally, this article provides an outlook on the future development of PLP-dependent enzymes, including in vivo regeneration system and industrial applications of PLP cofactors, and discusses the tremendous potential of these enzymes in biocatalytic applications.

Analysis of Calculated Liver Scores for Long-Term Outcome in 423 Cutaneous Melanoma Patients.

Background: Neoadjuvant and adjuvant therapies are currently getting increasingly important in cutaneous melanoma (CM) management. However, there is still a lack of prognostic tools to identify which patients have a poor prognosis. There is increasing evidence that the liver score may be a potential prognostic parameter in different tumour types. The aim was to investigate whether established liver scores can establish the prognosis of CM. Methods: According to established methods, the APRI, the MELD score, the MELD-Na score and the De Ritis ratio were calculated from the laboratory values at the time of the initial diagnosis. Survival was compared with the Kaplan-Meier curve and tested with log-rank tests. Risk factors associated with cutaneous melanoma-specific survival (CMSS) and progression-free survival (PFS) were assessed by using the Cox proportional hazards regression model. To determine the diagnostic accuracy, we performed a time-dependent ROC analysis. Results: A total of 423 patients were included, including 141 patients in AJCC stage (2017) I (33.3%), 82 in stage II (19.4%), 128 in stage III (30.3%) and 72 in stage IV (17%). Median time until melanoma-specific death was 99 months (IQR: 37-126). In addition, 37.6% of patients relapsed with a median time to relapse of 88 months (IQR: 17.5-126). In all stages, tumour thickness and ulceration were independent markers for predicting CMSS and PFS (p < 0.05). The multivariable analysis with all stages showed no significant association with CM outcome for liver scores (p > 0.05). The subgroup analysis revealed that the APRI (≥0.2241) was associated with CMSS and PFS in melanoma stages I and II, independently of tumour thickness, age and ulceration (HR 2.57, 95% CI 1.14-5.75; HR 2.94, 95% CI 1.42-6.09, respectively). Conclusions: The 20-year prognosis of AJCC stage I and II CM was dependent on tumour thickness and the APRI. High tumour thickness and an APRI ≥ 0.2241 at the initial diagnosis were associated with a worse prognosis. Future studies should investigate the independent prognostic value of the APRI in low-stage CM. Furthermore, the APRI score could be a potential biomarker for nomograms.

Development of a µPAD for the point-of-care testing of serum glutamic oxaloacetic transaminase (SGOT).

A wax-patterned paper analytical device (µPAD) has been developed for point-of-care colourimetric testing of serum glutamic oxaloacetic transaminase (SGOT). The detection method was based on the transamination reaction of aspartate with α-ketoglutarate, leading to the formation of oxaloacetate which reacts with the reagent Fast Blue BB salt and forms a cavern pink colour. The intensity of the cavern pink colour grows as the concentration of SGOT increases. UV-visible spectroscopy was utilized to optimize reaction conditions, and the optimized reagents were dropped onto the wax-patterned paper. The coloured PADs, after the addition of SGOT, have been photographed, and a colour band has been generated to correlate the SGOT concentration visually. The images were used to calculate the intensity values using ImageJ software, which inturn was used to calculate the SGOT concentration. The PADs were also tested with serum samples, and SGOT spiked serum samples. The PAD could detect the SGOT concentration ranging from 5 to 200 U/L. The analysis yielded highly accurate results with less than 6% relative error compared to the clinical sample. This colourimetric test demonstrated exceptional selectivity in the presence of other biomolecules in the blood serum, with a detection limit of 2.77 U/L and a limit of quantification of 9.25 U/L. Additionally, a plasma separation membrane was integrated with the PAD to directly test SGOT from finger-prick blood samples.

New transaminase from Odontosyllis undecimdonta the first potential enzyme of the luciferin biosynthesis pathway.

Among nearly a hundred known bioluminescent systems, only about a dozen have been studied to some extent, and the structures of only a few luciferins have been established. Moreover, the biosynthesis pathway is known only for two of them - the fungal and bacterial ones. Marine polychaetes of the Odontosyllis genus possess bright bioluminescence. The structures of its bioluminescence system key components were recently elucidated, and a possible pathway of the luciferin biosynthesis was proposed. Here we report the transaminase enzyme from Odontosyllis undecimdonta, the first potential participant of the cascade. We demonstrate that the discovered ferment catalyzes the transamination of the cys2DOPA, one of the potential luciferin biosynthetic precursors. The results of the experiments support the hypothesis that the discovered enzyme might be the part of the Odontosyllis luciferin biosynthesis pathway.

The AST/ALT ratio predicts survival and improves oncological therapy decisions in patients with non-small cell lung cancer receiving immunotherapy with or without radiotherapy.

Background and purpose: Immunotherapy, with or without radiotherapy (iRT or ICIs-nonRT), is the standard treatment for non-small cell lung cancer (NSCLC). Nonetheless, the response to the treatment varies among patients. Given the established role of aspartate aminotransferase/alanine transaminase (AST/ALT) ratio in predicting cancer prognosis, we sought to identify whether the pre-treatment AST/ALT ratio has the potential to serve as a prognostic factor for NSCLC patients receiving ICIs-nonRT and iRT. Materials and methods: We retrospectively analyzed NSCLC patients who received immunotherapy between April 2018 and March 2021. Patients were classified into iRT group and ICIs-nonRT group and further classified based on AST/ALT ratio cut-off values. The Kaplan-Meier (KM) method estimated the time-to-event endpoints (progression-free survival (PFS) and overall survival (OS). Results: Of the cohort, 239 underwent ICIs-nonRT and 155 received iRT. Higher AST/ALT ratios correlated with worse outcomes in the ICIs-nonRT group but indicated better outcomes in those who received iRT. Multivariate analysis validated AST/ALT ratio as an independent prognostic factor. For AST/ALT ratios between 0.67-1.7, both ICIs-nonRT and iRT yielded similar treatment outcomes; with AST/ALT ratios greater than 1.7, iRT could be a more favorable treatment option (P=0.038). Conversely, for ratios less than 0.67, ICIs-nonRT could be a more favorable treatment option (P=0.073). Conclusions: The pre-treatment AST/ALT ratio demonstrates potential as a prognostic marker for treatment outcomes in NSCLC patients receiving either ICIs-nonRT or iRT. This finding could help guide clinicians in selecting more effective treatment protocols, thereby enhancing patient prognosis.

Strong associations between fasting lipids and glucose concentrations and ALT levels strengthened with increasing ALT quantiles.

BACKGROUND: A persistent redox state and excessive reactive species involved in carbohydrate and lipid metabolism lead to oxidative damage in the liver, however, how fasting plasma concentrations of lipids and glucose are associated with fasting blood levels of alanine transaminase (ALT) and aspartate transaminase (AST) remains to be evaluated in large-scale population. METHODS: A cross-sectional study with 182,971 residents aged 18 to 92 years; multidimensional stratified analyses including quantile linear regression analysis and sex stratification were adopted to improve the quality of the evidence. RESULTS: The associations between the concentrations of non-HDL-C and triglyceride and ALT levels were positive, stronger in males in each quantile of ALT levels and the coefficients expanded with increasing ALT levels at slopes of 3.610 and 5.678 in males and 2.977 and 5.165 in females, respectively. The associations between the HDL-C concentrations and ALT levels were negative, also stronger in males in each quantile and the coefficients expanded with increasing ALT levels at slopes of -7.839 in females and - 5.797 in males. The associations between glucose concentrations and ALT levels were positive, but stronger in females in each quantile and the coefficients expanded with increasing ALT levels at slopes of 1.736 in males and 2.177 in females, respectively. Similar pattern consist of relatively weaker coefficients and slops were observed between concentrations of non-HDL-C, triglyceride and glucose and AST levels. The associations between albumin concentration and concentrations of blood lipids and glucose were relatively steady across all quantiles. CONCLUSIONS: The dose dependent effect between blood concentrations of lipids and glucose and liver function changes suggests that excessive carbohydrate and lipid metabolism may cause subclinical liver damage. Long term sustained primary and secondary inflammatory factors produced in the liver might be transmitted to adjacent organs, such as the heart, kidneys, and lungs, to cause and/or exacerbate pathological changes in these visceral organs.

Effectiveness and safety of tenofovir amibufenamide in chronic hepatitis B patients.

This letter to the editor relates to the study entitled "Tenofovir amibufenamide vs tenofovir alafenamide for treating chronic hepatitis B: A real-world study", which was recently published by Peng et al. Hepatitis B virus infection represents a significant health burden worldwide and can lead to cirrhosis and even liver cancer. The antiviral drugs currently used to treat patients with chronic hepatitis B infection still have many side effects, so it is crucial to identify safe and effective drugs to inhibit viral replication.

[Occupational chronic psychological stress and transaminase, HSP70 gene family and its proteins association of the interaction with metabolic syndrome].

OBJECTIVE: To explore the association of Occupational chronic psychological stress with transaminase, heat shock protein70(HSP70)gene family and their protein interaction with metabolic syndrome(MS). METHODS: A case-control study was used. According to the inclusion and exclusion criteria, from March 2015 to March 2016, 583 unrelated MS patients were selected as the case group and 585 unrelated healthy people as the control group among hospitalized and physical examination subjects aged 20-60 in Wuzhong People's Hospital and General Hospital of Ningxia Medical University. Questionnaire survey, physical examination, clinical and biochemical indicators, serum HSP70 level and five-locus polymorphism detection of HSP70 gene were carried out. GMDR 0.7 software was used to analyze the relationship between psychological stress, transaminase, HSP70 gene and its protein interaction and MS. RESULTS: After adjusting for age and sex, the rs1008438, rs1061581, rs539689 and rs222795 locus of HSP70 gene in the Co-dominant model and Dominant model and the rs222795 loci in the Over-dominant model carry wild homozygous genotype and heterozygous genotype were all related to the reduction of MS risk(OR<1, P<0.05). GMDR result: the 2-factor interaction model composed of psychological stress and serum HSP70, the 2-3 factor interaction model composed of transaminase activity, and the 2-6 factor interaction model composed of five locus of HSP70 gene, the 2-9 factor interaction model consisting of psychological stress and transaminase activity, HSP70 gene and its protein were all significantly associated with MS(P<0.01, P<0.05), all each factor interaction models were the best, and the 9-factor optimal interaction model had the highest risk of MS(OR=46.51, 95%CI 27.65-78.26), and the risk of MS in high-risk type was 45.23 times higher than that in low-risk type(95%CI 31.29-65.38, P<0.01). CONCLUSION: HSP70 gene family carrying wild-type alleles is a protective factor for MS. The interaction among Occupational chronic psychological stress interacts with transaminases, HSP70 gene and its serum proteins may be associated with MS. With the increase of involvement interaction factors, the risk of MS increased significantly. The interaction of multiple factors can greatly increase its risk.

Incidence of Elevated Liver Enzyme Levels in Patients Receiving Remdesivir and Its Effective Factors.

Background: Emergency use of remdesivir was approved for COVID-19 in some countries. Based on the promising results of remdesivir, the most common side effects were nausea, worsening respiratory failure, increased alanine aminotransferase levels, and constipation. The aim of this study was to determine the incidence of elevated liver enzymes in patients with COVID-19 receiving remdesivir. Methods: In this retrospective study, information was collected from patients' files. The study population included patients with moderate to severe COVID-19 who were admitted to Rouhani Babol Hospital. For daily patient selection, the list of patients was extracted from the system, and based on the census, the patient file was selected. Data were analyzed using Stata 16. Results: 620 patients suffering from moderate to severe COVID-19 were included in this study, 43% of whom were men. Of these patients, 120 were selected as the control group who did not receive remdesivir. The increase in liver enzymes in patients receiving remdesivir compared with the control, for alanine transaminase (ALT) and aspartate transaminase (AST), respectively, was 6.20 and 3.64 times, but it was not statistically significant for alkaline phosphatase (ALP). Also, the increase in bilirubin levels in patients receiving remdesivir was not statistically significant. Conclusion: The recipients of remdesivir had high liver enzymes, which is one of the possible side effects of this drug. The intensity of the enzymes was mild and moderate, and they were not dangerous to the health of any of the consumers. Deaths in patients with COVID-19 were not due to drug-induced liver complications but to other factors such as disease-related complications.

Semi-rational engineering of ω-transaminase for enhanced enzymatic activity to 2-ketobutyrate.

Transaminases (EC 2.6.1.X, TAs) are important biocatalysts in the synthesis of chiral amines, and have significant value in the field of medicine. However, TAs suffer from low enzyme activity and poor catalytic efficiency in the synthesis of chiral amines or non-natural amino acids, which hinders their industrial applications. In this study, a novel TA derived from Paracoccus pantotrophus (ppTA) that was investigated in our previous study was employed with a semi-rational design strategy to improve its enzyme activity to 2-ketobutyrate. By using homology modeling and molecular docking, four surrounding sites in the substrate-binding S pocket were selected as potential mutational sites. Through alanine scanning and saturation mutagenesis, the optimal mutant V153A with significantly improved enzyme activity was finally obtained, which was 578 % higher than that of the wild-type ppTA (WT). Furthermore, the mutant enzyme ppTA-V153A also exhibited slightly improved temperature and pH stability compared to WT. Subsequently, the mutant was used to convert 2-ketobutyrate for the preparation of L-2-aminobutyric acid (L-ABA). The mutant can tolerate 300 mM 2-ketobutyrate with a conversion rate of 74 %, which lays a solid foundation for the preparation of chiral amines.

Evaluation of elevated serum liver enzymes and metabolic syndrome in the PERSIAN Guilan cohort study population.

Objective: The purpose of this study is to evaluate the association between elevated serum liver enzymes and Metabolic Syndrome (MetS) in Prospective Epidemiological Research Studies of the Iranian Adults (PERSIAN) Guilan Cohort Study (PGCS) population. Methods: This cross-sectional study involved 10,519 individuals between the ages of 35 and 70 enrolled in the PGCS. The gathered data encompassed demographic information, anthropometric measurements, blood pressure, and biochemical indicators. MetS was defined by the National Cholesterol Education Program-Adult Treatment Panel III criteria (NCEP-ATP III). The associations between elevated liver enzymes and MetS were examined using logistic regression analysis. Odds ratio (OR) and 95 % confidence interval (CI) were calculated. Results: The prevalence of MetS was 41.8 %, and the prevalence of elevated alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), and alkaline phosphatase (ALP) were 19.4, 4.6, 11.6, and 5.1 %, respectively. In the unadjusted model, elevated ALT, AST, and GGT were associated with increased odds of MetS (OR = 1.55, 95 % CI: 1.41-1.71; OR = 1.29, 95 % CI: 1.07-1.55, and OR = 1.90, 95 % CI: 1.69-2.14, respectively). These associations remained significant for ALT and GGT after adjustment for some demographic and clinical characteristics (aOR = 1.31, 95 % CI: 1.17-1.46 and aOR = 1.30, 95 % CI: 1.14-1.49, respectively). In addition, the odds of MetS increased with the number of elevated liver enzymes, up to almost 1.32-fold among subjects with three/four elevated liver enzymes. Conclusion: The higher incidence of elevated liver enzymes was associated with an increased likelihood of MetS. Including liver markers in diagnosing and predicting MetS holds promise and is considered a possible approach.

Succinic semialdehyde dehydrogenase deficiency: a metabolic and genomic approach to diagnosis.

Genomic sequencing offers an untargeted, data-driven approach to genetic diagnosis; however, variants of uncertain significance often hinder the diagnostic process. The discovery of rare genomic variants without previously known functional evidence of pathogenicity often results in variants being overlooked as potentially causative, particularly in individuals with undifferentiated phenotypes. Consequently, many neurometabolic conditions, including those in the GABA (gamma-aminobutyric acid) catabolism pathway, are underdiagnosed. Succinic semialdehyde dehydrogenase deficiency (SSADHD, OMIM #271980) is a neurometabolic disorder in the GABA catabolism pathway. The disorder is due to bi-allelic pathogenic variants in ALDH5A1 and is usually characterized by moderate-to-severe developmental delays, hypotonia, intellectual disability, ataxia, seizures, hyperkinetic behavior, aggression, psychiatric disorders, and sleep disturbances. In this study, we utilized an integrated approach to diagnosis of SSADHD by examining molecular, clinical, and metabolomic data from a single large commercial laboratory. Our analysis led to the identification of 16 patients with likely SSADHD along with three novel variants. We also showed that patients with this disorder have a clear metabolomic signature that, along with molecular and clinical findings, may allow for more rapid and efficient diagnosis. We further surveyed all available pathogenic/likely pathogenic variants and used this information to estimate the global prevalence of this disease. Taken together, our comprehensive analysis allows for a global approach to the diagnosis of SSADHD and provides a pathway to improved diagnosis and potential incorporation into newborn screening programs. Furthermore, early diagnosis facilitates referral to genetic counseling, family support, and access to targeted treatments-taken together, these provide the best outcomes for individuals living with either GABA-TD or SSADHD, as well as other rare conditions.

Global lysine succinylation analysis unveils post-translational regulation effect on phenylpropanoid metabolism remodeling during Lonicera japonica flower development.

Lonicera japonica plays a significant role in traditional Chinese medicine and as a food source, making it a focus of studies on protein succinylation and its potential role in regulating secondary metabolism during flower development. This study aimed to clarify the regulatory mechanism of protein succinylation on phenylpropanoid-related phenotypic changes by conducting a global lysine succinylation proteomic analysis across different flowering stages. A total of 586 lysine succinylated peptides in 303 proteins were identified during early and late floral stages. Functional enrichment analysis revealed that succinylated proteins primarily participated in the tricarboxylic acid (TCA) cycle, amino acid metabolism, and secondary metabolism. The abundance of succinylated aspartate transaminase (AT), 4-coumarate-CoA ligase (4CL), and phenylalanine N-hydroxylase (CYP79A2) in phenylpropanoid metabolism varied during flower development. In vitro experiments demonstrated that succinylation increased AT activity while inhibited 4CL activity. Decreased levels of total flavonoids and phenolic acids indicated significant alterations in phenylpropanoid metabolism during later floral stages. These results suggest that succinylation of TCA cycle proteins not only influences flower development but also, together with AT-4CL-CYP79A2 co-succinylation, redirects phenylpropanoid metabolism during flower development in L. japonica.

Identification of Kibdelomycin and Related Biosynthetic Gene Clusters and Characterization of the C-Branching of Amycolose.

Many bacterial natural products contain C-branched sugars, including components from the outer cell wall or antibiotically active metabolites. The enzymatic C-branching of keto sugars leading to longer side chains (≥C2) is catalyzed by thiamine diphosphate (ThDP)-dependent enzymes. Chiral tertiary α-hydroxy ketones are formed in this process. The ThDP-dependent enzymes that catalyze C-branching reactions belong to one of three enzymatic superfamilies: decarboxylases, transketolases, and α-ketoacid dehydrogenases 2, but branching of keto sugars has only been demonstrated for decarboxylases. In this study, we showed that an α-ketoacid dehydrogenase is responsible for C-branching of the deoxyketo sugar amycolose in the biosynthesis of kibdelomycin in Kibdelosporangium sp. MA7385. In addition, we characterized an amino transferase in the same biosynthetic gene cluster (BGC) that accepts a sterically demanding tertiary α-hydroxy ketone in a downstream reaction. Subsequently, we identified approximately 400 similar BGCs in silico, suggesting that there is a large diversity of possible ThDP-dependent enzymes catalyzing the C-branching of keto sugars and subsequent modifications.

Efficiently manufacturing ectoine via metabolic engineering and protein engineering of L-2,4-diaminobutyrate transaminase.

Ectoine, so-called tetrahydropyrimidine, is an important osmotic adjustment solute and widely applied in cosmetics and protein protectant. Some attempts have been made to improve the ectoine productivity. However, the strains with both high ectoine production capacity and high glucose conversion were still absent so far. Aim to construct a strain for efficiently producing ectoine, ectoine synthetic gene cluster ectABC from Pseudomonas stutzeri was overexpressed in E. coli BL21 (DE3). The ection production was improved by 382 % (ectoine titer increased from 1.73 g/L to 8.33 g/L) after the rational design of rate-limiting enzyme L-2,4-diaminobutyrate transaminase EctBps (protein engineering) combined with the metabolic engineering that focused on the enrichment and conversion of precursors. The final strain YW20 was applied to overproduce ectoine in fed-batch fermentation and yield 68.9 g/L of ectoine with 0.88 g/L/h of space-time yield and the highest glucose conversion reported [34 % (g/g)]. From the fermentation broth, ectoine was purified with 99.7 % purity and 79.8 % yield. This study successfully provided an engineered strain as well as an efficient method for the industrial bio-synthesis and preparation of ectoine.

Anthocyanins as Adjuvant Treatment for Non-alcoholic Fatty Liver Disease: A Systematic Review and Meta-Analysis.

Recent studies suggest a role for anthocyanins in the treatment of non-alcoholic fatty liver disease (NAFLD). The purpose of the present review was to assess the effect of anthocyanins as an adjuvant treatment in patients with NAFLD. The literature search was conducted on MEDLINE/PubMed, the Cochrane Central Register of Controlled Trials (CENTRAL), the Web of Science, and Scopus without language or time limits up to March 27, 2024. The primary outcomes included the severity of liver fibrosis and the level of liver transaminases. Secondary outcomes included obesity and lipid profile assessments. Standardized mean differences (SMDs) with 95% CIs were calculated for numerical outcomes. Five studies were included. The pooled effect sizes showed lower levels of liver fibrosis and liver transaminases in the anthocyanin group, but the difference was nonsignificant and small in size. The same result was obtained with anthropometric measurements of total cholesterol, low-density lipoprotein, and serum triglycerides, where effect sizes ranged from negligible to medium in magnitude but were all nonsignificant. The anthocyanin group showed a significantly lower body fat percentage (SMD = -0.41 (95%CI: -0.76; -0.06), P = 0.021). Currently, no evidence is available on the efficacy of anthocyanins in improving liver fibrosis or dyslipidemia in patients with NAFLD. There is limited evidence that anthocyanins can lower body fat percentages, but the effect was not reflected in the pooled results of other obesity indices. The few available clinical trials showed several limitations and variations regarding the doses of anthocyanins. Future clinical trials should avoid the limitations of the current studies and provide evidence supporting or refuting the use of anthocyanins in NAFLD patients.

BCAT1 promotes cell proliferation, migration, and invasion via the PI3K-Akt signaling pathway in oral squamous cell carcinoma.

OBJECTIVES: To analyze the expression, biological function of branched chain amino-acid transaminase 1 (BCAT1) in oral squamous cell carcinoma (OSCC). MATERIALS AND METHODS: Real-time PCR and immunohistochemistry were used to analyze the expression of BCAT1 protein in OSCC and normal oral tissues. Based on the clinicopathological information of patients, the relationship between the expression of BCAT1 protein and other clinicopathological factors was analyzed. Real-time PCR and western blot assays were used to analyze the expression of BCAT1 gene and protein in normal human oral keratinocytes (HOK) and human OSCC cells, respectively. After BCAT1 overexpression or knockdown, the proliferation, cell cycle, migration, and invasion of human OSCC cells were analyzed by CCK8, flow cytometry, wound healing, and transwell invasion assays, respectively. After adding the BCAT1 inhibitor EGR240 to OSCC cells, the changes in cell proliferation, migration, and invasion ability in OSCC cells were analyzed. Based on the TCGA database, the involved signal pathway in BCAT1-related and BCAT1-binding genes was obtained for Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, verified by western blot assays. After inhibiting PI3K, the effect of BCAT1 on the expression of the downstream phosphorylated protein of the PI3K-Akt signaling pathway was analyzed by western blot assays. The relationship between the expression of BCAT1 and EMT-related protein of OSCC cells was also analyzed. RESULTS: The expression of BCAT1 gene and protein were upregulated in OSCC tissue, which positively correlated with the pathological grade of patients with OSCC. Compared with normal oral keratinocytes, BCAT1 gene and protein were upregulated in OSCC cells. BCAT1 overexpression promoted the proliferation, migration, and invasion of OSCC cells. BCAT1 knockdown or inhibition could reduce the proliferation, migration, and invasion abilities of OSCC cells. The results of bioinformatics analysis and Western bolt showed that BCAT1 could regulate the activation of PI3K-Akt signaling pathway, and promote epithelial-mesenchymal transition (EMT) of OSCC cells. CONCLUSIONS: BCAT1 could promote the proliferation, migration, and invasion of OSCC cells via PI3K-Akt signaling pathway, which is a potential therapeutic target for OSCC.

Tuning of Protein Expression by Promoter Engineering.

The promoter is an essential component of an expression system since it regulates the transcriptional beginning of related genes. The optimal expression level can be achieved by employing a promoter engineering approach. Typically, creating a library of T7 promoters allows for titratable protein expression. In the process of making ß-amino acid (sitagliptin intermediate) from ß-keto ester, esterase from Pseudomonas stutzeri (Est PS) is used to convert the ß-keto ester to ß-keto acid. Subsequently, transaminase from Ilumatobacter coccineus (TAIC) transforms the ß-keto acid to its corresponding ß-amino acid. Here, we describe the optimization of the expression levels of Est PS for the maximum production of sitagliptin intermediate. The different promoter strengths for Est PS were built into the T7 promoters of the pET15b vector. With the help of these new co-expressing entire cells, the expressed enzyme ratio for each enzyme was determined. As the strength of the promoter of Est PS decreases, the expression level also decreases (from 100% to 10%). Conversely, the TAIC expression level is increased. This developed system produced a higher sitagliptin intermediate than enzymes' unoptimized expression level.

Combining binding pocket mutagenesis and substrate tunnel engineering to improve an (R)-selective transaminase for the efficient synthesis of (R)-3-aminobutanol.

(R)-selective transaminases have the potential to act as efficient biocatalysts for the synthesis of important pharmaceutical intermediates. However, their low catalytic efficiency and unfavorable equilibrium limit their industrial application. Seven (R)-selective transaminases were identified using homologous sequence mining. Beginning with the optimal candidate from Mycolicibacterium hippocampi, virtual mutagenesis and substrate tunnel engineering were performed to improve catalytic efficiency. The obtained variant, T282S/Q137E, exhibited 3.68-fold greater catalytic efficiency (kcat/Km) than the wild-type enzyme. Using substrate fed-batch and air sweeping processes, effective conversion of 100 mM 4-hydroxy-2-butanone was achieved with a conversion rate of 93 % and an ee value > 99.9 %. This study provides a basis for mutation of (R)-selective transaminases and offers an efficient biocatalytic process for the asymmetric synthesis of (R)-3-aminobutanol.

Immobilization of His6-tagged amine transaminases in microreactors using functionalized nonwoven nanofiber membranes.

Process intensification is crucial for industrial implementation of biocatalysis and can be achieved by continuous process operation in miniaturized reactors with efficiently immobilized biocatalysts, enabling their long-term use. Due to their extremely large surface-to-volume ratio, nanomaterials are promising supports for enzyme immobilization. In this work, different functionalized nanofibrous nonwoven membranes were embedded in a two-plate microreactor to enable immobilization of hexahistidine (His6)-tagged amine transaminases (ATAs) in flow. A membrane coated with Cu2+ ions gave the best results regarding His6-tagged ATAs immobilization among the membranes tested yielding an immobilization yield of up to 95.3 % for the purified N-His6-ATA-wt enzyme. Moreover, an efficient one-step enzyme immobilization process from overproduced enzyme in Escherichia coli cell lysate was developed and yielded enzyme loads up to 1088 U mL-1. High enzyme loads resulted in up to 80 % yields of acetophenone produced from 40 mM (S)-α-methylbenzylamine in less than 4 min using a continuously operated microreactor. Up to 81 % of the initial activity was maintained in a 5-day continuous microreactor operation with immobilized His6-tagged ATA constructs. The highest turnover number within the indicated time was 7.23·106, which indicates that this immobilization approach using advanced material and reactor system is highly relevant for industrial implementation.