Worm-Based Diagnosis Combining Microfluidics toward Early Cancer Screening.

Early cancer diagnosis increases therapy efficiency and saves huge medical costs. Traditional blood-based cancer markers and endoscopy procedures demonstrate limited capability in the diagnosis. Reliable, non-invasive, and cost-effective methods are in high demand across the world. Worm-based diagnosis, utilizing the chemosensory neuronal system of C. elegans, emerges as a non-invasive approach for early cancer diagnosis with high sensitivity. It facilitates effectiveness in large-scale cancer screening for the foreseeable future. Here, we review the progress of a unique route of early cancer diagnosis based on the chemosensory neuronal system of C. elegans. We first introduce the basic procedures of the chemotaxis assay of C. elegans: synchronization, behavior assay, immobilization, and counting. Then, we review the progress of each procedure and the various cancer types for which this method has achieved early diagnosis. For each procedure, we list examples of microfluidics technologies that have improved the automation, throughput, and efficiency of each step or module. Finally, we envision that microfluidics technologies combined with the chemotaxis assay of C. elegans can lead to an automated, cost-effective, non-invasive early cancer screening technology, with the development of more mature microfluidic modules as well as systematic integration of functional modules.

Effects of 5-aminolevulinic acid photodynamic therapy for cervical low-grade squamous intraepithelial lesions with HR-HPV infections.

Objective: To determine the effectiveness and safety of 5-aminolevulinic acid mediated photodynamic therapy (5-ALA PDT) in HR-HPV infected patients with cervical low-grade squamous intraepithelial lesions (LSIL) and to explore possible factors affecting treatment outcomes. Methods: This retrospective study included 96 patients with histologically confirmed cervical LSIL and high-risk human papillomavirus (HR-HPV) infection. They received 5-ALA PDT treatment once a week for a total of 3 courses. All patients were evaluated by cytology tests, HPV DNA assay, colposcopy, and biopsy at 2 weeks, 3 months, and 6 months checkpoint. The chi-square test were used to evaluate the differences in various clinical data, and a p value <0.05 was considered statistically significant. Results: At 2 weeks, 3 months, and 6 months checkpoint, colposcopies showed that the cervical iodine-unstained area under VILI (visual inspection with Lugol's iodine) significantly reduced (p < 0.01) with no structure changes. At 3 months and 6 months checkpoint, the pathological regression rate reached 87.5% (84/96) and 94.79% (91/96), while the HR-HPV clearance rates reached 80.21% (77/96) and 93.75% (90/96) respectively. We also examined the efficacy in the HPV 16/18-related group and non-HPV 16/18-related group. The HR-HPV clearance rate in the HPV16/18 group [94.87% (37/39)] was significantly higher than that of the non-HPV 16/18 group [70.17% (40/57)]. However, at 6 months after treatment, the clearance rate of the HPV 16/18 group [94.87% (37/39)] showed no statistical difference from the non-HPV 16/18 group [92.30% (53/57)]. Conclusion: Topical 5-ALA PDT can effectively eliminate HR-HPV infection and treat low-grade cervical squamous intraepithelial lesions, it offers an alternative treatment option for patients with LSIL, especially for those with fertility requirements and who wish to preserve cervical structure or function.

Profile analysis and functional modeling identify circular RNAs in nonalcoholic fatty liver disease as regulators of hepatic lipid metabolism.

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease, associated with an outcome of hepatic fibrosis/cirrhosis and hepatocellular carcinoma. However, limited exploration of the underlying mechanisms hinders its prevention and treatment. To investigate the mechanisms of epigenetic regulation in NAFLD, the expression profile of circular RNA (circRNA) of rodents in which NAFLD was induced by a high-fat, high-cholesterol (HFHC) diet was studied. Modeling of the circRNA-microRNA (miRNA) -mRNA regulatory network revealed the functional characteristics of NAFLD-specific circRNAs. The targets and effects in the liver of such NAFLD-specific circRNAs were further assessed. Our results uncovered that the downregulation of 28 annotated circRNAs characterizes HFHC diet-induced NAFLD. Among the downregulated circRNAs, long intergenic non-protein coding RNA, P53 induced transcript (LNCPINT) -derived circRNAs (circ_0001452, circ_0001453, and circ_0001454) targeted both miR-466i-3p and miR-669c-3p. Their deficiency in NAFLD abrogated the circRNA-based inhibitory effect on both miRNAs, which further inactivated the AMPK signaling pathway via AMPK-α1 suppression. Inhibition of the AMPK signaling pathway promotes hepatic steatosis, depending on the transcriptional and translational upregulation of lipogenic genes, such as those encoding sterol regulatory element-binding protein 1 (SREBP1) and fatty acid synthase (FASN) in hepatocytes. The levels of LNCPINT-derived circRNAs displayed a negative association with hepatic triglyceride (TG) concentration. These findings suggest that loss of LNCPINT-derived circRNAs may underlie NAFLD via miR-466i-3p- and miR-669c-3p-dependent inactivation of the AMPK signaling pathway.

Process study of ceramic membrane-coupled mixed-cell fermentation for the production of adenine.

In order to solve the problems of high complexity, many by-products, high pollution and difficult extraction of the existing adenine production process, in this study, ceramic membrane-coupled mixed cell fermentation was used to produce adenine while reducing the synthesis of by-products and simplifying the production process of adenine. Nucleoside hydrolase (encoded by the rihC gene) was used to produce adenine by coordinated fermentation with the adenosine-producing bacterium Bacillus Subtilis XGL. The adenosine hydrolase (AdHy)-expressing strain Escherichia coli BL21-AdHy was successfully employed and the highest activity of the crude enzyme solution was found by orthogonal experiments at 170 W power, 42% duty cycle, and 8 min of sonication. The highest AdHy activity was found after 18 h of induction incubation. E. coli BL21-AdHy was induced for 18 h and sonicated under the above ultrasonic conditions and the resulting crude enzyme solution was used for co-fermentation of the strain and enzyme. Moreover, 15% (v/v) of the AdHy crude enzyme solution was added to fermentation of B. subtilis XGL after 35 h. Finally, the whole fermentation system was dialyzed using coupled ceramic membranes for 45 and 75 h, followed by the addition of fresh medium. In contrast, the AdHy crude enzyme solution was added after 35, 65, and 90 h of B. subtilis fermentation, with three additions of 15, 15, and 10% of the B. subtilis XGL fermentation system. The process was validated in a 5 L fermenter and 14 ± 0.25 g/L of adenine was obtained, with no accumulation of adenosine and d-ribose as by-products. The enzymatic activity of the AdHy crude solution treated with ultrasound was greatly improved. It also reduced the cellular activity of E. coli BL21-AdHy and reduced effects on bacterial co-fermentation. Membrane-coupled dialysis solved the problem of decreased yield due to poor bacterial survival and decreased viability, and eliminated inhibition of the product synthesis pathway by adenosine. The batch addition of crude enzyme broth allowed the continuous conversion of adenosine to adenine. This production method provides the highest yield of biologically produced adenine reported to date, reduces the cost of adenine production, and has positive implications for the industrial production of adenine by fermentation. And it provides a reference for producing other high-value-added products made by fermentation.

Curcumin alleviates aristolochic acid nephropathy based on SIRT1/Nrf2/HO-1 signaling pathway.

Aristolochic acid I (AA-I), presenting in a variety of natural medicinal plants, which could cause tubular epithelial cell injury. Curcumin (CUR), a polyphenolic substance isolated from turmeric, is a natural antioxidant. The aim of this experiment was to investigate whether CUR attenuated AA-I-induced renal injury in rats through the SIRT1/Nrf2/HO-1 signaling pathway. SD rats were treated with AA-I (10 mg/kg) or/and CUR (200 mg/kg) for 28 days to assess the protective effect of CUR on AA-I-induced renal injury in vivo. NRK-52E cells were treated with AA-I (40 µ M) or/and CUR (20 µ M) for 24 h in vitro. The intervention pathway of CUR against oxidative stress injury induced by AA-I was assessed by observing pathological changes, oxidative stress status, apoptosis and the expression of SIRT1/Nrf2/HO-1 signaling pathway-related factors. The results showed that AA-I exposure increased the contents of BUN, Cr, KIM-1, NGAL, ALT and AST in serum. It increased the content of MDA, decreased the activities of SOD, GST, GSH and the content of ATP in renal tissue. Pathological changes such as inflammatory cell infiltration and mitochondrial injury occurred in renal tissue. AA-I exposure resulted in a substantial rise in the levels of BAX, Ccaspase-9, Cleaved Caspase-9, Caspase-3, Cleaved Caspase-3 and a significant decrease in mRNA and protein expression levels of Bcl-2, SIRT1, Nrf2, NQO1, HO-1 and Keap1. However, these changes were reversed by CUR intervention. In summary, AA-I exposure caused mitochondrial dysfunction and triggered apoptosis through the oxidative stress pathway. However, CUR could reduce AA-I-induced renal injury by activating the SIRT1/Nrf2/HO-1 signaling pathway.

Accelerating glioblastoma therapeutics via venture philanthropy.

Development of curative treatments for glioblastoma (GBM) has been stagnant in recent decades largely because of significant financial risks. A portfolio-based strategy for the parallel discovery of breakthrough therapies can effectively reduce the financial risks of potentially transformative clinical trials for GBM. Using estimates from domain experts at the National Brain Tumor Society (NBTS), we analyze the performance of a portfolio of 20 assets being developed for GBM, diversified across different development phases and therapeutic mechanisms. We find that the portfolio generates a 14.9% expected annualized rate of return. By incorporating the adaptive trial platform GBM AGILE in our simulations, we show that at least one drug candidate in the portfolio will receive US Food and Drug Administration (FDA) approval with a probability of 79.0% in the next decade.

Effects of chronic HBV infection on lipid metabolism in non-alcoholic fatty liver disease: A lipidomic analysis.

INTRODUCTION AND OBJECTIVES: Chronic hepatitis B virus (HBV) infection exerts an impact on lipid metabolism, but its interaction with dysmetabolism-based non-alcoholic fatty liver disease (NAFLD) remains uncertain. The purpose of the study was to investigate the effects of HBV infection on lipid metabolism, hepatic steatosis and related impairments of NAFLD patients. METHODS: Biopsy-proven Chinese NAFLD patients with (NAFLD-HBV group, n = 21) or without chronic HBV infection (NAFLD group, n = 41) were enrolled in the case-control study. Their serum lipidomics was subjected to individual investigation by ultra-performance liquid chromatography-tandem mass spectrometry. Steatosis, activity, and fibrosis (SAF) scoring revealed the NAFLD-specific pathological characteristics. RESULTS: Chronic HBV infection was associated with global alteration of serum lipidomics in NAFLD patients. Upregulation of phosphatidylcholine (PCs), choline plasmalogen (PC-Os) and downregulation of free fatty acids (FFAs), lysophosphatidylcholine (LPCs) dominated the HBV-related lipidomic characteristics. Compared to those of NAFLD group, the levels of serum hepatoxic lipids (FFA16:0, FFA16: 1, FFA18:1, FFA18:2) were significantly lowered in the NAFLD-HBV group. These low-level FFAs demonstrated correlation to statistical improvements in aspartate aminotransferase activity (FFA16:0, r = 0.33; FFA16:1, r = 0.37; FFA18:1, r = 0.32; FFA18:2, r = 0.42), hepatocyte steatosis (FFA16: 1, r = 0.39; FFA18:1, r = 0.39; FFA18:2, r = 0.32), and ballooning (FFA16:0, r = 0.30; FFA16:1, r = 0.45; FFA18:1, r = 0.36; FFA18:2, r = 0.30) (all P < 0.05). CONCLUSION: Chronic HBV infection may impact on the serum lipidomics and steatosis-related pathological characteristics of NAFLD.

APOC3 rs2070667 Associates with Serum Triglyceride Profile and Hepatic Inflammation in Nonalcoholic Fatty Liver Disease.

Single-nucleotide polymorphisms (SNPs) of apolipoprotein C3 (APOC3) play important role in lipid metabolism, and dyslipidemia underlies nonalcoholic fatty liver disease (NAFLD). But the correlation of serum lipidomics, APOC3 SNPs, and NAFLD remains limited understood. Enrolling thirty-four biopsy-proven NAFLD patients from Tianjin, Shanghai, Fujian, we investigated their APOC3 genotype and serum lipid profile by DNA sequencing and ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), respectively. Scoring of hepatocyte steatosis, ballooning, lobular inflammation, and liver fibrosis was then performed to reveal the role of lipidomics-affecting APOC3 SNPs in NAFLD-specific pathological alterations. Here, we reported that APOC3 SNPs (rs4225, rs4520, rs5128, rs2070666, and rs2070667) intimately correlated to serum lipidomics in NAFLD patients. A allele instead of G allele at rs2070667, which dominated the SNPs underlying lipidomic alteration, exhibited downregulatory effect on triacylglycerols (TGs: TG 54 : 7, TG 54 : 8, and TG 56 : 9) containing polyunsaturated fatty acid (PUFA). Moreover, subjects with low-level PUFA-containing TGs were predisposed to high-grade lobular inflammation (TG 54 : 7, rho = -0.454 and P = 0.007; TG 54 : 8, rho = -0.411 and P =0.016; TG 56 : 9, rho = -0.481 and P = 0.004). The significant correlation of APOC3 rs2070667 and inflammation grading [G/G vs. G/A+A/A: 0.00 (0.00 and 1.00) vs. 1.50 (0.75 and 2.00), P = 0.022] further confirmed its pathological action on the basis of lipidomics-impacting activity. These findings suggest an inhibitory effect of A allele at APOC3 rs2070667 on serum levels of PUFA-containing TGs, which are associated with high-grade lobular inflammation in NAFLD patients.

Efficient fermentative production of L-theanine by Corynebacterium glutamicum.

L-Theanine is a unique non-protein amino acid found in tea plants that has been shown to possess numerous functional properties relevant to food science and human nutrition. L-Theanine has been commercially developed as a valuable additive for use in food and beverages, and its market is expected to expand substantially if the production cost can be lowered. Although the enzymatic approach holds considerable potential for use in L-theanine production, demand exists for developing more tractable methods (than those currently available) that can be implemented under mild conditions and will reduce operational procedures and cost. Here, we sought to engineer fermentative production of L-theanine in Corynebacterium glutamicum, an industrially safe host. For L-theanine synthesis, we used γ-glutamylmethylamide synthetase (GMAS), which catalyzes the ATP-dependent ligation of L-glutamate and ethylamine. First, distinct GMASs were expressed in C. glutamicum wild-type ATCC 13032 strain and GDK-9, an L-glutamate overproducing strain, to produce L-theanine upon ethylamine addition to the hosts. Second, the L-glutamate exporter in host cells was disrupted, which markedly increased the L-theanine titer in GDK-9 cells and almost eliminated the accumulation of L-glutamate in the culture medium. Third, a chromosomally gmasMm-integrated L-alanine producer was constructed and used, attempting to synthesize ethylamine endogenously by expressing plant-derived L-serine/L-alanine decarboxylases; however, these enzymes showed no L-alanine decarboxylase activity under our experimental conditions. The optimal engineered strain that we ultimately created produced ~ 42 g/L L-theanine, with a yield of 19.6%, in a 5-L fermentor. This is the first report of fermentative production of L-theanine achieved using ethylamine supplementation.

Removing the by-products acetic acid and NH4 + from the L-tryptophan broth by vacuum thin film evaporation during L-tryptophan production

Background: During L-tryptophan production by Escherichia coli, the by-products, acetic acid and NH4 +, accumulate in the fermentation broth, resulting in inhibited cell growth and activity and decreased L-tryptophan production. To improve the L-tryptophan yield and glucose conversion rate, acetic acid and NH4 + were removed under low-temperature vacuum conditions by vacuum scraper concentrator evaporation; the fermentation broth after evaporation was pressed into another fermenter to continue fermentation. To increase the volatilisation rate of acetic acid and NH4 + and reduce damage to bacteria during evaporation, different vacuum evaporation conditions were studied. Results: The optimum operating conditions were as follows: vacuum degree, 720 mm Hg; concentration ratio, 10%; temperature, 60°C; and feeding rate, 300 mL/min. The biomass yield of the control fermentation (CF) and fermentation by vacuum evaporation (VEF) broths was 55.1 g/L and 58.3 g/L at 38 h, respectively, (an increase of 5.8%); the living biomass yield increased from 8.9 (CF) to 10.2 pF (VEF; an increase of 14.6%). L-tryptophan production increased from 50.2 g/L (CF) to 60.2 g/L (VEF) (an increase of 19.9%), and glucose conversion increased from 18.2% (CF) to 19.5% (VEF; an increase of 7.1%). The acetic acid concentrations were 2.74 g/L and 6.70 g/L, and the NH4 + concentrations were 85.3 mmol/L and 130.9 mmol/L in VEF and CF broths, respectively. Conclusions: The acetic acid and NH4 + in the fermentation broth were quickly removed using the vacuum scraper concentrator, which reduced bacterial inhibition, enhanced bacterial activity, and improved the production of L-tryptophan and glucose conversion rate.

SIRT7 antagonizes TGF-ß signaling and inhibits breast cancer metastasis.

Distant metastasis is the main cause of breast cancer-related death; however, effective therapeutic strategies targeting metastasis are still scarce. This is largely attributable to the spatiotemporal intratumor heterogeneity during metastasis. Here we show that protein deacetylase SIRT7 is significantly downregulated in breast cancer lung metastases in human and mice, and predicts metastasis-free survival. SIRT7 deficiency promotes breast cancer cell metastasis, while temporal expression of Sirt7 inhibits metastasis in polyomavirus middle T antigen breast cancer model. Mechanistically, SIRT7 deacetylates and promotes SMAD4 degradation mediated by ß-TrCP1, and SIRT7 deficiency activates transforming growth factor-ß signaling and enhances epithelial-to-mesenchymal transition. Significantly, resveratrol activates SIRT7 deacetylase activity, inhibits breast cancer lung metastases, and increases survival. Our data highlight SIRT7 as a modulator of transforming growth factor-ß signaling and suppressor of breast cancer metastasis, meanwhile providing an effective anti-metastatic therapeutic strategy.Metastatic disease is the major reason for breast cancer-related deaths; therefore, a better understanding of this process and its players is needed. Here the authors report the role of SIRT7 in inhibiting SMAD4-mediated breast cancer metastasis providing a possible therapeutic avenue.

Strategy for enhancing adenosine production under the guidance of transcriptional and metabolite pool analysis.

OBJECTIVES: To rationally identify targets for enhancing adenosine production, transcription level of genes involved in adenosine synthesis of Bacillus subtilis XGL was detected during the fermentation process, complemented with metabolite pool analysis. RESULTS: PurR-regulated genes (pur operon and purA) and prs were down-regulated and 5-phosphoribosyl 1-pyrophosphate (PRPP) decreased considerably after 24 h when adenosine significantly accumulated. Since PRPP could strongly antagonize the binding of PurR to its targets, it was inferred that down-regulation of pur operon and purA might be due to a low PRPP pool, which was confirmed by metabolite analysis. So desensitized prs responsible for PRPP synthesis was overexpressed, resulting in increased PRPP concentration and pur operon transcription. To further enhance the adenosine production, desensitized purF and prs were co-overexpressed with integrating additional copy of purA to B. subtilis XGL genome, resulting in 24.3 % (1.29 g/g DCW) higher adenosine production than that by B. subtilis XG. CONCLUSIONS: Overexpression of prs, purF and purA under the guidance of transcriptional and metabolite pool analysis significantly increased adenosine production. Strategies used in this study have potential applications for rational modification of industrial microorganisms.

Reducing lactate secretion by ldhA Deletion in L-glutamate- producing strain Corynebacterium glutamicum GDK-9

L-lactate is one of main byproducts excreted in to the fermentation medium. To improve L-glutamate production and reduce L-lactate accumulation, L-lactate dehydrogenase-encoding gene ldhA was knocked out from L-glutamate producing strain Corynebacterium glutamicum GDK-9, designated GDK-9ΔldhA. GDK-9ΔldhA produced approximately 10.1% more L-glutamate than the GDK-9, and yielded lower levels of such by-products as α-ketoglutarate, L-lactate and L-alanine. Since dissolved oxygen (DO) is one of main factors affecting L-lactate formation during L-glutamate fermentation, we investigated the effect of ldhA deletion from GDK-9 under different DO conditions. Under both oxygen-deficient and high oxygen conditions, L-glutamate production by GDK-9ΔldhA was not higher than that of the GDK-9. However, under micro-aerobic conditions, GDK-9ΔldhA exhibited 11.61% higher L-glutamate and 58.50% lower L-alanine production than GDK-9. Taken together, it is demonstrated that deletion of ldhA can enhance L-glutamate production and lower the unwanted by-products concentration, especially under micro-aerobic conditions.

[Modification in de novo purine pathway for adenosine accumulation by Bacillus subtilis].

OBJECTIVE: To study the effects of co-overexpression of purF, purM, purN, purH and purD genes on adenosine production in Bacillus subtilis. METHODS: First, an extra purF gene under control of the P43 promoter was integrated into the B. subtilis chromosome at the native purF locus by single crossover, resulting in simultaneous expression of purF, purM, purN, purH and purD. Then the transcriptional levels of the five genes in the engineering strain were tested by Realtime Quantitative PCR. The activity of PRPP amidotransferase was also detected. Finally, cell growth, glucose consumption and adenosine production in engineering strain along with original strain were examined. RESULTS: The transcriptional analysis showed that purF and its downstream genes purM, purN, purH and purD were simultaneously upregulated at different level. The PRPP amidotransferase activity of engineering strain was about 2.4-fold that of original strain. Shake flask fermentation showed the improvement in adenosine yield and conversion ratio from glucose to adenosine (17.5% and 26.1%, respectively). Fed-batch fermentation by the engineering strain was conducted. Compared with the original strain, adenosine accumulation of engineering strain increased within the same fermentation time. However, the cell growth of engineering strain was retarded. CONCLUSION: The co-overexpression of purF and its downstream genes purM, purN, purH and purD could enhance the adenosine yield in the culture broth. This paper could facilitate future research by providing theoretical evidence and method of metabolic engineering.

[Metformin improves epididymal sperm quality and antioxidant function of the testis in diet-induced obesity rats].

OBJECTIVE: To observe the effects of metformin on epididymal sperm quality and antioxidant function of the testis in diet-induced obesity rats. METHODS: Thirty-two male SD rats were fed on high-fat food for 8 weeks to make obesity models, and another 8 were included as normal controls. Twenty-four of the model rats were equally randomized into a model control group to be fed continuously on high-fat food, a metformin group to be fed on normal food with metformin, and a normal food group. By the end of the 12th week, all the rats were killed for the determination of Lee's index, the organ coefficients of the testis and epididymis, epididymal sperm concentration, sperm motility, grade a + b sperm percentage, and the contents of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and malondialdehyde (MDA) in the testicular homogenate. RESULTS: Lee's index was significantly increased in the model control group (P < 0.01) as compared with the other three. Lee's index was markedly higher in the normal control than in the metformin group (P < 0.05). The organ coefficients of the testis and epididymis were significantly decreased in the model control group (P < 0.01) as compared with the other three. Sperm concentration and motility and the percentage of a + b sperm were significantly decreased in the model control in comparison with the other three groups (P < 0.05 or P < 0.01). Sperm concentration was remarkably higher in the normal control than in the metformin and normal food groups (P < 0.05). The content of SOD (U/mg prot) was significantly lower in the model control (90.92 +/- 4.06) than in the normal control and metformin groups (101.69 +/- 8.49 and 102.04 +/- 10.67) (P < 0.05); that of GSH-Px (U) obviously higher in the normal control (28.32 +/- 2.28) than in the model control (23.49 +/- 1.08, P < 0.01), the metformin (25.73 +/- 2.14, P < 0.05) and the normal food group (25.77 +/- 2.19, P < 0.05), but evidently lower in the model control than in the metformin group (P < 0.05); and that of MDA (nmol/mg prot) significantly higher in the model control (2.68 +/- 0.76) than in the normal control (1.84 +/- 0.31, P < 0.01), the metformin (1.88 +/- 0.33, P < 0.01), and the normal food group (2.14 +/- 0.35, P < 0.05). CONCLUSION: Metformin therapy and improved diet could improve sperm quality and promote the antioxidant ability of the testis in diet-induced obesity rats.

[Molecular cloning, gene expression and characterization of purine nucleoside phosphorylase from Pseudoalteromonas sp. XM2107].

OBJECTIVE: Purine nucleoside phosphorylase (PNP, EC 2.4.2.1) is an important enzyme which is applied in nucleoside medication and intermediate biosynthesis. In this paper, we aimed to obtain the PNP gene from cold-adapted marine bacterium Pseudoalteromonas sp. XM2107 and study the characteristics of enzyme for applying in nucleoside medication and intermediate biosynthesis. METHODS: Purine nucleoside phosphorylas gene which amplified from the cold-adapted marine bacterium Pseudoalteromonas sp. XM2107 genome by homology-based PCR cloning was cloned, sequenced and expressed at E. coli BL21 (DE3) by using expression vector pET-His. The recombinant purine nucleoside phosphorylas enzyme (XmPNP) was purified by metal chelate chromatography and its several characteristics were determined completely. RESULTS: Analysis of entire sequences of XmPNP revealed that the whole sequence is 702 bp and coded a peptide of 233 amino acids with a calculated molecular mass of 25 kDa. Compared with mesophilic counterparts, XmPNP showed a lower temperature optimum (50 degrees C). The optimal pH for inosine phosphorolysis catalyzed by XmPNP was around 7.6 at sodium phosphate buffer. XmPNP showed the highest activity toward inosine (K(m) value, 0.382 mmol/L, at 37 degrees C) and the activity decreased in the order of guanosine and adenosine. Furthermore, XmPNP still expressed high catalytic activity and excellent thermalstability at ordinary temperature. CONCLUSION: Both high catalytic activity and good thermalstability at ordinary temperature indicated that it will provide attractive candidate for prodrug activation and nucleoside medication biotransformation.