Predictive nomograms based on gamma-glutamyl transpeptidase to prealbumin ratio for prognosis of hepatocellular carcinoma patients without microvascular invasion.

BACKGROUND: Hepatocellular carcinoma (HCC) presents a significant threat to individuals and healthcare systems due to its high recurrence rate. Accurate prognostic models are essential for improving patient outcomes. Gamma-glutamyl transpeptidase (GGT) and prealbumin (PA) are biomarkers closely related to HCC. This study aimed to investigate the predictive value of the GGT to PA ratio (GPR) and to construct prognostic nomograms for HCC patients without microvascular invasion. METHODS: We retrospectively analyzed data from 355 HCC patients who underwent radical hepatectomy at Shengjing Hospital of China Medical University between December 2012 and January 2021. Patients were randomly assigned to a training cohort (n = 267) and a validation cohort (n = 88). The linearity of GPR was assessed using restricted cubic spline (RCS) analysis, and the optimal cut-off value was determined by X-tile. Kaplan-Meier survival curves and log-rank tests were used to investigate the associations between GPR and both progression-free survival (PFS) and overall survival (OS). Cox multivariate regression analysis identified independent risk factors, enabling the construction of nomograms. Time-dependent receiver operating characteristic (ROC) and calibration curves were used to evaluate the accuracy of the nomograms. Decision curve analysis (DCA) assessed the predictive value of the models. RESULTS: Patients were categorized into GPR-low and GPR-high groups based on a GPR value of 333.33. Significant differences in PFS and OS were observed between the two groups (both P < 0.001). Cox multivariate analysis identified GPR as an independent risk factor for both PFS (OR = 1.80, 95% CI: 1.24-2.60, P = 0.002) and OS (OR = 1.87, 95% CI: 1.07-3.26, P = 0.029). The nomograms demonstrated good predictive performance, with C-index values of 0.69 for PFS and 0.76 for OS. Time-dependent ROC curves and calibration curves revealed the accuracy of the models in both the training and validation cohorts, with DCA results indicating notable clinical value. CONCLUSIONS: GPR emerged as an independent risk factor for both OS and PFS in HCC patients without microvascular invasion. The nomograms based on GPR demonstrated relatively robust predictive efficiency for prognosis.

GGT5: a potential immunotherapy response inhibitor in gastric cancer by modulating GSH metabolism and sustaining memory CD8+ T cell infiltration.

PURPOSE: The variable responses to immunotherapy observed in gastric cancer (GC) patients can be attributed to the intricate nature of the tumor microenvironment. Glutathione (GSH) metabolism significantly influences the initiation and progression of gastric cancer. Consequently, targeting GSH metabolism holds promise for improving the effectiveness of Immune checkpoints inhibitors (ICIs). METHODS: We investigated 16 genes related to GSH metabolism, sourced from the MSigDB database, using pan-cancer datasets from TCGA. The most representative prognosis-related gene was identified for further analysis. ScRNA-sequencing analysis was used to explore the tumor heterogeneity of GC, and the results were confirmed by  Multiplex immunohistochemistry (mIHC). RESULTS: Through DEGs, LASSO, univariate and multivariate Cox regression analyses, and survival analysis, we identified GGT5 as the hub gene in GSH metabolism with the potential to promote GC. Combining CIBERSORT, ssGSEA, and scRNA analysis, we constructed the immune architecture of GC. The subpopulations of T cells were isolated, revealing a strong association between GGT5 and memory CD8+ T cells. Furthermore, specimens from 10 GC patients receiving immunotherapy were collected. mIHC was used to assess the expression levels of GGT5 and memory CD8+ T cell markers. Our results established a positive correlation between GGT5 expression, the enrichment of memory CD8+ T cells, and a suboptimal response to immunotherapy. CONCLUSIONS: Our study identifies GGT5, a hub gene in GSH metabolism, as a potential therapeutic target for inhibiting the response to immunotherapy in GC patients. These findings offer new insights into strategies for optimizing immunotherapy of GC.

The γ-glutamyl cycle serves as an amino acids supply system in colorectal cancer organoids under chronic hypoxia.

Malignant tumors are characterized by a hypoxic microenvironment, and metabolic reprogramming is necessary to ensure energy production and oxidative stress resistance. Although the microenvironmental properties of tumors vary under acute and chronic hypoxia, studies on chronic hypoxia-induced metabolic changes are limited. In the present study, we performed a comprehensive metabolic analysis in a chronic hypoxia model using colorectal cancer (CRC) organoids, and identified an amino acid supply system through the γ-glutamyl cycle, a glutathione recycling pathway. We analyzed the metabolic changes caused by hypoxia over time and observed that chronic hypoxia resulted in an increase in 5-oxoproline and a decrease in oxidized glutathione (GSSG) compared to acute hypoxia. These findings suggest that chronic hypoxia induces metabolic changes in the γ-glutamyl cycle. Moreover, inhibition of the γ-glutamyl cycle via γ-glutamyl cyclotransferase (GGCT) and γ-glutamyl transferase 1 (GGT1) knockdown significantly reversed chronic hypoxia-induced upregulation of 5-oxoproline and several amino acids. Notably, GGT1 knockdown downregulated the intracellular levels of γ-glutamyl amino acids. Conclusively, these results indicate that the γ-glutamyl cycle serves as an amino acid supply system in CRC under chronic hypoxia, which provides fresh insight into cancer metabolism under chronic hypoxia.

Biotin-tagged fluorescent probe for in situ visualization of γ-glutamyl transpeptidase in cancerous cells and tissues.

γ-Glutamyl transpeptidase (GGT), a cell-surface enzyme, is strongly implicated in mammalian malignancy growth and migration processes including human hepatocarcinogens. However, simply and conveniently detect of GGT on the cell membrane remains highly challenging. In this study, a biotin-tagged fluorescent probe Nap-biotin-glu was developed using glutamic acid, naphthalimide, and biotin as the reaction site, fluorescent reporter, and membrane-targeting group, which required only three steps. Colocalization fluorescence imaging and immunofluorescence analysis indicated that probe Nap-biotin-glu was successfully realized in situ visualizing of GGT on the cell membrane.Owing to the significant over-expressed GGT level in tumor, the probe was successfully applied to distinguish cancer tissues from adjacent normal tissues.

Sensory properties of rehydrated Toona sinensis shoots after dehydrated by different drying methods and association with gamma-glutamyl transferase reaction.

Sulfur-containing compounds are responsible for the aroma of Toona sinensis shoot (TS). In this study, vacuum-freeze-drying (VFD), microwave-drying (MD), and hot-air-drying at 100 and 40 °C (HAD100 and HAD40, respectively), were applied to dehydrate perishable TS for preservation. VFD-TS retained most aroma of fresh/raw TS after rehydration. The content of sulfur-containing compounds reached to 118.00 µg/g with leading by methyl thiirane, (E,E)/(E,Z)/(Z,Z)-bis-(1-propenyl) disulfides, and (Z)/(E)-2-mercapto-3,4-dimethyl-2,3-dihydrothiophenes accounting for 86.33 %. They were undetected in the rehydrated MD-TS and HAD100-TS, as the indigenous enzymes in TS were deactivated under their dehydration conditions. Interestingly, the sulfur-containing compounds was restored by 77.47 % after the TS was treated by gamma-glutamyl transferase (GGT). Thus, the release of sulfur-containing compounds from TS could depend on GGT reaction. It was different from alliaceous vegetables relying on alliinase reaction. The results revealed the aroma formation in TS and provided an approach to enhance the aroma of TS dried by different methods.

Mitocytosis Mediated by an Enzyme-Activable Mitochondrion-Disturbing Polymer-Drug Conjugate Enhances Active Penetration in Glioblastoma Therapy.

The application of nanomedicines for glioblastoma (GBM) therapy is hampered by the blood-brain barrier (BBB) and the dense glioblastoma tissue. To achieve efficient BBB crossing and deep GBM penetration, this work demonstrates a strategy of active transcellular transport of a mitochondrion-disturbing nanomedicine, pGBEMA22-b-pSSPPT9 (GBEPPT), in the GBM tissue through mitocytosis. GBEPPT is computer-aided designed and prepared by self-assembling a conjugate of an amphiphilic block polymer and a drug podophyllotoxin (PPT). When GBEPPT is delivered to the tumor site, overexpressed γ-glutamyl transpeptidase (GGT) on the brain-blood endothelial cell, or the GBM cell triggered enzymatic hydrolysis of γ-glutamylamide on GBEPPT to reverse its negative charge to positive. Positively charged GBEPPT rapidly enter into the cell and target the mitochondria. These GBEPPT disturb the homeostasis of mitochondria, inducing mitocytosis-mediated extracellular transport of GBEPPT to the neighboring cells via mitosomes. This intracellular-to-intercellular delivery cycle allows GBEPPT to penetrate deeply into the GBM parenchyma, and exert sustainable action of PPT released from GBEPPT on the tumor cells along its penetration path at the tumor site, thus improving the anti-GBM effect. The process of mitocytosis mediated by the mitochondrion-disturbing nanomedicine may offer great potential in enhancing drug penetration through malignant tissues, especially poorly permeable solid tumors.

Efficient expression of γ-glutamyl transpeptidase in Bacillus subtilis via CRISPR/Cas9n and its immobilization.

In this study, we successfully applied the strategy of combining tandem promoters and tandem signal peptides with overexpressing signal peptidase to efficiently express and produce γ-glutamyl peptidase (GGT) enzymes (BsGGT, BaGGT, and BlGGT) from Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus licheniformis in Bacillus subtilis ATCC6051Δ5. In order to avoid the problem of instability caused by duplicated strong promoters, we assembled tandem promoters of different homologous genes from different species. To achieve resistance marker-free enzyme in the food industry, we first removed the replication origin and corresponding resistance marker of Escherichia coli from the expression vector. The plasmid was then transformed into the B. subtilis host, and the Kan resistance gene in the expression plasmid was directly edited and silenced using the CRISPR/Cas9n-AID base editing system. As a result, a recombinant protein expression carrier without resistance markers was constructed, and the enzyme activity of the BlGGT strain during shake flask fermentation can reach 53.65 U/mL. The recombinant BlGGT was immobilized with epoxy resin and maintained 82.8% enzyme activity after repeated use for 10 times and 87.36% enzyme activity after storage at 4 °C for 2 months. The immobilized BlGGT enzyme was used for the continuous synthesis of theanine with a conversion rate of 65.38%. These results indicated that our approach was a promising solution for improving enzyme production efficiency and achieving safe production of enzyme preparations in the food industry. KEY POINTS: • Efficient expression of recombinant proteins by a combination of dual promoter and dual signal peptide. • Construction of small vectors without resistance markers in B. subtilis using CRISPR/Cas9n-AID editing system. • The process of immobilizing BlGGT with epoxy resin was optimized.

Prediction of Early Atherosclerotic Plaques Using a Sequence-Activated Fluorescence Probe for the Simultaneous Detection of γ-Glutamyl Transpeptidase and Hypobromous Acid.

Atherosclerosis is a lipoprotein-driven disease, and there is no effective therapy to reverse atherosclerosis or existing plaques. Therefore, it is urgently necessary to create a noninvasive and reliable approach for early atherosclerosis detection to prevent initial plaque formation. Atherosclerosis is intimately associated with inflammation, which is accompanied by an excess of reactive oxygen species (ROS), leading to cells requiring more glutathione (GSH) to resist severe oxidative stress. Therefore, the GSH-hydrolyzed protein γ-glutamyl transpeptidase (GGT) and the ROS-hypobromous acid (HBrO) are potential biomarkers for predicting atherogenesis. Hence, to avoid false-positive diagnoses caused by a single biomarker, we constructed an ingenious sequence-activated double-locked TP fluorescent probe, C-HBrO-GGT, in which two sequential triggers of GGT and HBrO are meticulously designed to ensure that the probe fluoresces in response to HBrO only after GGT hydrolyzes the probe. By utilization of C-HBrO-GGT, the voltage-gated chloride channel (CLC-1)-HBrO-catalase (CAT)-GGT signaling pathway was confirmed in cellular level. Notably, the forthcoming atherosclerotic plaques were successfully predicted before the plaques could be observed via the naked eye or classical immunofluorescent staining. Collectively, this research proposed a powerful tool to indicate the precise position of mature plaques and provide early warning of atherosclerotic plaques.

Exposure to phthalates and their alternatives in relation to biomarkers of inflammation and oxidative stress in adults: evidence from NHANES 2017-2018.

Phthalates and their alternatives are considered significant environmental risk factors that potentially influence inflammation and oxidative stress. However, their impact on biomarkers of inflammation and oxidative stress was inconsistent. This study aimed to explore the associations between phthalates and high-sensitivity C-reactive protein (hsCRP), gamma-glutamyl transferase (GGT), and white blood cell (WBC) counts, employing both univariate exposure and multivariate co-exposure models. For this analysis, a total of 1619 individuals aged 18 years and above, sourced from the National Health and Nutrition Examination Survey (NHANES) conducted between 2017 and 2018, were selected as subjects. We explored the associations between hsCRP, GGT, and WBC counts and eighteen different phthalate metabolites. Multiple linear regression analysis revealed significant associations between both MCNP and MEHP and hsCRP. We observed negative correlations of MCOP, MCPP, MHBP, and MONP with GGT. Conversely, MEHHP and MEHHTP exhibited positive correlations with GGT. Furthermore, MECPTP and MEHHTP showed positive correlations with WBC. Notably, we identified a non-linear relationship between phthalates and inflammation and oxidative stress markers. The Bayesian kernel machine regression (BKMR) analysis demonstrated a negative joint effect of the phthalates mixture on GGT, particularly at lower concentrations. The BKMR model also found that MEOHP and MHiBP were negatively associated with GGT. In contrast, MEHHP showed a significant positive association with GGT. Moderating effect analysis suggested that dietary inflammatory index (DII), income-to-poverty ratio (PIR), age, BMI, and physical activity influenced the association between phthalates and inflammation and oxidative stress. These findings contribute to a deeper understanding of the relationships between phthalates and inflammation and oxidative stress.

Association between liver enzymes and metabolic syndrome: a study in Bangladeshi adults.

BACKGROUND: This study aimed to investigate the association between serum liver enzymes and the presence of metabolic syndrome (MetS) among Bangladeshi adults. RESEARCH DESIGN AND METHODS: A total of 602 participants (424 males and 178 females) were enrolled in this cross-sectional study. Serum levels of liver enzymes (ALT, AST, GGT and ALP) and other biochemical parameters were measured by standard colorimetric methods. The relationship between liver enzymes and MetS was assessed by multivariable logistic regression models. RESULTS: Overall, the prevalence of MetS was 34.9% among the participants. Of the four liver enzymes, the mean levels of serum ALT and GGT were significantly higher among subjects with MetS than those without MetS (p < 0.01). When liver enzyme levels were categorized into normal and elevated ranges, MetS and its component's prevalence was higher in the elevated group except for ALP. Serum ALT and GGT showed a significant relationship with the maximum components of MetS. According to the logistic regression analysis, elevated levels of ALT and GGT were significantly associated with the prevalence of MetS (p < 0.01 and p < 0.001, respectively). CONCLUSIONS: This study showed that elevated ALT and GGT levels were independently associated with MetS and its components.

Targeting gamma-glutamyl transpeptidase: A pleiotropic enzyme involved in glutathione metabolism and in the control of redox homeostasis.

Gamma-glutamyl transpeptidase (GGT) is an enzyme located on the outer membrane of the cells where it regulates the metabolism of glutathione (GSH), the most abundant intracellular antioxidant thiol. GGT plays a key role in the control of redox homeostasis, by hydrolyzing extracellular GSH and providing the cell with the recovery of cysteine, which is necessary for de novo intracellular GSH and protein biosynthesis. Therefore, the upregulation of GGT confers to the cell greater resistance to oxidative stress and the advantage of growing fast. Indeed, GGT is upregulated in inflammatory conditions and in the progression of various human tumors and it is involved in many physiological disorders related to oxidative stress, such as cardiovascular disease and diabetes. Currently, increased GGT expression is considered a marker of liver damage, cancer, and low-grade chronic inflammation. This review addresses the current knowledge on the structure-function relationship of GGT, focusing on human GGT, and provides information on the pleiotropic biological role and relevance of the enzyme as a target of drugs aimed at alleviating oxidative stress-related diseases. The development of new GGT inhibitors is critically discussed, as are the advantages and disadvantages of their potential use in clinics. Considering its pleiotropic activities and evolved functions, GGT is a potential "moonlighting protein".

Expression and characterization of C-terminal truncated mutants of γ-glutamyltranspeptidase II (PaGGTII) from Pseudomonas aeruginosa PAO1.

The gene encoding γ-glutamyltranspeptidase II (PaGGTII) from Pseudomonas aeruginosa PAO1 was cloned in Escherichia coli. Recombinant PaGGTII showed a weak activity (0.0332 U/mg), and it can be easily inactivated. Multiple alignment of microbial GGTs showed the redundancy of the C-terminal of the small subunit of PaGGTII in length. The truncation of eight amino acid residues at the C-terminal of PaGGTII remarkably improved the activity and stability of the enzyme (PaGGTIIΔ8; 0.388 U/mg). Further truncation at the C-terminal also provided the enzyme relatively higher activity (PaGGTIIΔ9, -Δ10, -Δ11, and -Δ12). Among C-terminal truncated mutants, we focused on PaGGTIIΔ8 and examined the effect of C-terminal amino acid residues on the properties of PaGGTIIΔ8 because the activity of PaGGTII was found to be greatly improved when 8 amino acid residues were truncated. Various mutant enzymes with different C-terminal amino acid residues were constructed. They were expressed in E. coli and purified to homogeneity by ion-exchange chromatography. The properties of PaGGTIIΔ8 and the mutants obtained from mutation at E569 were characterized. Km and kcat of PaGGTIIΔ8 for γ-glutamyl-p-nitroanilide (γ-GpNA) were 8.05 mM and 15.49 s-1, respectively. PaGGTIIΔ8E569Y showed the highest catalytic efficiency for γ-GpNA with a kcat/Km of 12.55 mM-1 s-1. Mg2+, Ca2+, and Mn2+ exhibited positive effects on the catalytic activity for PaGGTIIΔ8 and its ten E569 mutants.

Parenteral Nutrition, Sepsis, Acute Heart Failure and Hepatotoxic Drugs Are Related to Liver Test Disturbances in Critically Ill Patients.

BACKGROUND: Parenteral nutrition (PN) is often associated with liver dysfunction in the ICU, although other factors such as sepsis, acute heart failure (AHF), and hepatotoxic drugs can be equally present. The relative impact of PN on liver dysfunction in critically ill patients is largely unknown. METHODS: We recorded the presence of pre-existing liver disturbances, AHF, sepsis, daily PN volume, and commonly used hepatotoxic drugs in adult ICU patients, together with daily aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyltransferase (GGT), alkalic phosphatase (AP), total bilirubin (TB), and INR values in patients with three or more PN treatment days. A linear mixed-effects model was used to assess the relative contribution of each liver parameter. Nutritional adequacy was defined as intake/needs. RESULTS: We included 224 ICU patients with PN treatment lasting more than 3 days between 1 January 2017 and 31 December 2019. For AST, pre-existing liver disturbances (+180% ± 11%) and the presence of AHF (+75% ± 14%) were the main predictors of deterioration, whereas PN volume caused only a limited increase of 14% ± 1%/L. Similar results were observed for ALT. GGT, INR, and TB are mainly influenced by the presence of sepsis/septic shock and pre-existing liver disturbances, with no impact of PN or hepatotoxic drugs. Carbohydrate intake exceeded recommendations, and protein and lipid intake were insufficient in this study cohort. CONCLUSIONS: Liver test disturbances in ICU patients on PN are multifactorial, with sepsis and AHF having the highest influence, with only limited impact from PN and hepatotoxic drugs. Feeding adequacy can be improved.

Redesign of γ-glutamyl transpeptidase from Bacillus subtilis for high-level production of L-theanine by cavity topology engineering.

L-Theanine is a multifunctional nonprotein amino acid found naturally in tea leaves. It has been developed as a commercial product for a wide range of applications in the food, pharmaceutical, and healthcare industries. However, L-theanine production catalyzed by γ-glutamyl transpeptidase (GGT) is limited by the low catalytic efficiency and specificity of this class of enzymes. Here, we developed a strategy for cavity topology engineering (CTE) based on the cavity geometry of GGT from B. subtilis 168 (CGMCC 1.1390) to obtain an enzyme with high catalytic activity and applied it to the synthesis of L-theanine. Three potential mutation sites, M97, Y418, and V555, were identified using the internal cavity as a probe, and residues G, A, V, F, Y, and Q, which may affect the shape of the cavity, were obtained directly by computer statistical analysis without energy calculations. Finally, 35 mutants were obtained. The optimal mutant Y418F/M97Q showed a 4.8-fold improvement in catalytic activity and a 25.6-fold increase in catalytic efficiency. The recombinant enzyme Y418F/M97Q exhibited a high space-time productivity of 15.4 g L-1 h-1 by whole-cell synthesis in a 5 L bioreactor, which was one of the highest concentrations reported so far at 92.4 g L-1. Overall, this strategy is expected to enhance the enzymatic activity associated with the synthesis of L-theanine and its derivatives.Key points • Cavity topology engineering was used to modify the GGT for L-theanine biocatalysis. • The catalytic efficiency of GGT was increased by 25.6-fold. • Highest productivity of L-theanine reached 15.4 g L -1 h-1 (92.4 g L-1) in a 5 L bioreactor.

Biochemical and Hematological Indexes of Liver Dysfunction in Horses.

In the present review, the authors, based on the multiple functions performed by the liver, analyze the multiple biochemical and hematological changes as an expression of altered liver function in the horse. The liver performs important metabolic functions related to the synthesis, degradation, and excretion of various substances. Modification of these functions can be evaluated and diagnosed by determining serum concentrations of several serum analytes, including enzymes and other endogenous substances. Hepatocellular enzymes, such as sorbitol dehydrogenase-SDH and glutamate dehydrogenase-GLDH, are released following hepatocellular necrosis. Hepatobiliary enzymes, such as γ-glutamyl transferase-GGT, increase in response to necrosis, cholestasis, and other alterations in bile conducts. Serum concentrations of mainly endogenous and exogenous substances that the liver should synthesize or eliminate, such as proteins (albumin and globulins), bile acids, urea, glucose, total and direct bilirubin, and coagulation factors, and fibrinogen should be included in the liver function test profile. The interpretation of laboratory tests of liver function will allow the diagnosis of functional loss of the organ. Some of the analytes considered provide information on the prognosis of liver disease. This review will provide an accurate and objective interpretation of the common biochemical and hematological tests in use in the diagnosis of equine hepatic disease patients, aiding still further the veterinary activity on the applied equine clinical cases.

γ-Glutamyl-transpeptidase CsGGT2 functions as light-activated theanine hydrolase in tea plant (Camellia sinensis L.).

Theanine is an important secondary metabolite endowing tea with umami taste and health effects. It is essential to explore the metabolic pathway and regulatory mechanism of theanine to improve tea quality. Here, we demonstrated that the expression patterns of CsGGT2 (γ-glutamyl-transpeptidase), participated in theanine synthesis in vitro in our previous research, are significantly different in the aboveground and underground tissues of tea plants and regulated by light. Light up-regulated the expression of CsHY5, directly binding to the promoter of CsGGT2 and acting as an activator of CsGGT2, with a negative correlation with theanine accumulation. The enzyme activity assays and transient expression in Nicotiana benthamiana showed that CsGGT2, acting as bifunctional protein, synthesize and degrade theanine in vitro and in planta. The results of enzyme kinetics, Surface plasmon resonance (SPR) assays and targeted gene-silencing assays showed that CsGGT2 had a higher substrate affinity of theanine than that of ethylamine, and performed a higher theanine degradation catalytic efficiency. Therefore, light mediates the degradation of theanine in different tissues by regulating the expression of the theanine hydrolase CsGGT2 in tea plants, and these results provide new insights into the degradation of theanine mediated by light in tea plants.

First Example of the Extracellular Surface Expression of Intrinsically Periplasmic Escherichia coli γ-Glutamyltranspeptidase, a Member of the N-Terminal Nucleophile Hydrolase Superfamily, and the Use of Cells as a Catalyst for γ-Glutamylvalylglycine Production.

Although the purified Escherichia coli γ-glutamyltranspeptidase has much higher transpeptidation activity than hydrolysis activity, almost all γ-glutamyltranspeptidase activity is hydrolysis activity in vivo, that is when measured using the whole cells. By using the Met1 to Arg232 fragment of E. coli YiaT or the CapA of Bacillus subtilis subsp. Natto as an anchor protein, we succeeded in expressing E. coli γ-glutamyltranspeptidase on the extracellular surface of the cells, and these cells showed higher transpeptidation activity than hydrolysis activity in the presence of NaCl. Furthermore, E. coli cells overexpressing γ-glutamyltranspeptidase without an anchor from the T5 promoter maintained γ-glutamyltranspeptidase on the extracellular surface of the cells immediately after being harvested from the culture medium, but the enzyme was released from the extracellular surface of the cells subsequently in the absence of NaCl. Using these cells expressing γ-glutamyltranspeptidase on the extracellular surface, γ-Glu-Val-Gly, a kokumi compound, was successfully produced.

Degradation of glutathione and glutathione conjugates in plants.

Glutathione (GSH) is a ubiquitous, abundant, and indispensable thiol for plants that participates in various biological processes, such as scavenging reactive oxygen species, redox signaling, storage and transport of sulfur, detoxification of harmful substances, and metabolism of several compounds. Therefore knowledge of GSH metabolism is essential for plant science. Nevertheless, GSH degradation has been insufficiently elucidated, and this has hampered our understanding of plant life. Over the last five decades, the γ-glutamyl cycle has been dominant in GSH studies, and the exoenzyme γ-glutamyl transpeptidase has been regarded as the major GSH degradation enzyme. However, recent studies have shown that GSH is degraded in cells by cytosolic enzymes such as γ-glutamyl cyclotransferase or γ-glutamyl peptidase. Meanwhile, a portion of GSH is degraded after conjugation with other molecules, which has also been found to be carried out by vacuolar γ-glutamyl transpeptidase, γ-glutamyl peptidase, or phytochelatin synthase. These findings highlight the need to re-assess previous assumptions concerning the γ-glutamyl cycle, and a novel overview of the plant GSH degradation pathway is essential. This review aims to build a foundation for future studies by summarizing current understanding of GSH/glutathione conjugate degradation.

Serum liver enzymes and metabolic syndrome from the Rafsanjan Cohort Study.

Our investigation aimed at evaluating the relationship between metabolic syndrome, alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma glutamyl transferase (GGT), and alkaline phosphatase (ALP) in the Rafsanjan cohort study (RCS). We used data obtained from the RCS, as a part of the prospective epidemiological research studies in Iran. In this cross-sectional research, 9895 participants from the baseline phase of RCS who completed medical questionnaire were included. Metabolic syndrome (MetS) defined using NCEP-ATP III criteria. The relationship between elevated serum liver enzymes levels even within the normal range and metabolic syndrome was evaluated by logistic regressions. The prevalence of MetS was 34.42% in the participants of study. The mean concentrations of AST, ALT, ALP, and GGT increased with increasing MetS components. After adjusting for all potential confounders, elevated serum concentrations of ALT, AST, GGT, and ALP even within the normal range were related with an increased odds of MetS. MetS was associated with increased levels of liver enzymes even within the normal range. These results indicated the potential for elevated liver enzymes as biomarkers for the possible presence of MetS.

Association between Fasting and Postprandial Levels of Liver Enzymes with Metabolic Syndrome and Suspected Prediabetes in Prepubertal Children.

Elevated liver enzyme activity may be associated with metabolic syndrome (MetS); however, it is not included in the MetS definition for children. Postprandial changes in the levels of biochemistry tests are related to manifestations of metabolic abnormalities. We assessed the association between fasting and postprandial liver enzymes levels with MetS and elevated hemoglobin A1c (HbA1c) in children aged 9-11. The study included 51 girls and 48 boys, all presumably healthy. In all participants' anthropometric indices, fasting glucose, insulin, lipid profile and HbA1c were measured. Enzymes, including alanine aminotransferase (ALT) and gamma-glutamyl transferase (GGT), were assayed in fasting and postprandial states. Individuals were divided into subgroups: with (MetS(+): n = 26); without MetS (MetS(-): n = 73); with HbA1c levels ≤ 5.3% (n = 39); and ≥5.7% (n = 11). Elevated fasting GGT levels were found in 23% of MetS(+) children and rarely in MetS(-) children; increased postprandial GGT was noted in 35% of MetS(+) individuals. Postprandial GGT changes tend to predict MetS (OR = 1.16; p = 0.092). Increased fasting ALT was found rarely in MetS(+) children, but did not occur in MetS(-) children. HbA1c ≥ 5.7% occurred rarely and neither fasting ALT nor GGT were related to elevated HbA1c. However, postprandial change of ALT was a good positive predictor of increased HbA1c (OR = 1.33; p = 0.021). Postprandial GGT performs better as an indicator of metabolic syndrome occurrence, and instead postprandial ALT may predict prediabetes in prepubertal children.