Transaminases are a class of enzymes that catalyze the transfer of amino between amino acids and keto acids, playing an important role in the biosynthesis of organic amines and the corresponding derivatives. However, natural enzymes often have low catalytic efficiency against non-natural substrates, which limits their widespread applications. Enzyme engineering serves as an effective approach to improve the catalytic properties and thereby expand the application scope of transaminases. In this study, a high-throughput screening method for transaminases was established based on the fluorescent color reaction between methoxy-2-aminobenzoxime (PMA) and ketones. According to the changes in fluorescence intensity, the concentration changes of ketones could be easily monitored. The efficiency, sensitivity, and accuracy of the screening method were improved by optimization of the system. With 4-hydroxy-2-butanone as the substrate, the mutant library of the transaminase from Actinobacteria sp. was established and a mutant with increased activity was successfully obtained, which improved the production efficiency of (R)-3-aminobutanol by enzyme-catalyzed synthesis. This study laid an important foundation for efficient screening, modification, and application of transaminase.
Transaminases/metabolism* ; Fluorescent Dyes/chemistry* ; High-Throughput Screening Assays/methods* ; Ketones/metabolism* ; Actinobacteria/enzymology*

L-theanine is an important natural non-protein amino acid that is widely used in food and medicine. Although in previous studies, a microbial fermentation method for L-theanine without the addition of ethylamine has been developed, the conversion rate of this process needs to be further improved. In this study, we constructed a de novo synthesis pathway of L-theanine with glucose as the substrate. First, an in vitro transformation pathway containing ω-transaminase (TA) and γ-glutamylmethylamide synthetase (GMAS) was designed, optimized, and introduced into the chassis strain Escherichia coli K12 W3110 to achieve de novo synthesis of L-theanine. To improve the synthesis efficiency through metabolic engineering, we increased the copies of the GMAS gene gams and the TA gene spuC and enhanced the expression of the aldehyde dehydrogenase gene eutE to provide sufficient acetaldehyde substrate, knocked out the lactate dehydrogenase gene ldhA and the pyruvate formate lyase gene pflB to block bypass metabolism, and introduced the alanine dehydrogenase gene alD to recycle alanine. Furthermore, we over-expressed the phosphoenolpyruvate carboxylase gene ppc to enhance the carbon flux of the TCA cycle, knocked out the succinyl-CoA synthase gene sucCD to reduce the loss of downstream flux of TCA, and integrated the glutamate dehydrogenase gene gdh to enhance the supply of L-glutamate. Finally, the polyphosphate kinase gene ppk was introduced to the ATP cycle, which enhanced the energy supply in L-theanine production. The recombinant strain Tea11 produced 22.60 g/L L-theanine in a 5 L fermenter in 28 h, with a conversion rate of 41.71%. This synthetic pathway in this study balanced the relationship between the supply of ethylamine and the production of theanine, providing a new idea for metabolic engineering of microorganisms to produce L-theanine.
Glutamates/biosynthesis* ; Metabolic Engineering/methods* ; Escherichia coli/genetics* ; Fermentation ; Transaminases/metabolism* ; Amide Synthases/metabolism* ; Glucose/metabolism*

L-phosphinothricin (L-PPT) is an efficient broad-spectrum herbicide. To realize the multi-enzyme catalytic preparation of L-PPT, we constructed an engineered strain Escherichia coli YM-1 for efficient expression of D-amino acid transaminase, which could catalyze the generation of the intermediate 2-oxo-4-[(hydroxymethylphosphonyl)] butyric acid (PPO) from D-phosphinothricin (D-PPT). In addition, E. coli pLS was constructed to co-express glutamate dehydrogenase and glucose dehydrogenase, which not only catalyzed the generation of L-PPT from PPO but also regenerated the coenzyme nicotinamide adenine dinucleotide phosphate (NADPH). A fed-batch fermentation process was then established for E. coli YM-1 and pLS, and the apparent activities of D-amino acid transaminase and glutamate dehydrogenase were increased by 22.68% and 100.82%, respectively, compared with those in shake flasks. The process parameters were optimized for the catalytic preparation of L-PPT by whole-cell cascade of E. coli YM-1 and pLS with D, L-PPT as the substrate. After reaction for 8 h, 91.36% conversion of D-PPT was achieved, and the enantiomeric excess of L-PPT reached 90.22%. The findings underpin the industrial production of L-PPT.
Escherichia coli/enzymology* ; Aminobutyrates/metabolism* ; Glutamate Dehydrogenase/biosynthesis* ; Glucose 1-Dehydrogenase/biosynthesis* ; Herbicides/metabolism* ; Multienzyme Complexes/metabolism* ; Transaminases/metabolism* ; Phosphinic Acids/metabolism*

ω-transaminase (ω-TA) is a natural biocatalyst that has good application potential in the synthesis of chiral amines. However, the poor stability and low activity of ω-TA in the process of catalyzing unnatural substrates greatly hampers its application. To overcome these shortcomings, the thermostability of (R)-ω-TA (AtTA) from Aspergillus terreus was engineered by combining molecular dynamics simulation assisted computer-aided design with random and combinatorial mutation. An optimal mutant AtTA-E104D/A246V/R266Q (M3) with synchronously enhanced thermostability and activity was obtained. Compared with the wild- type (WT) enzyme, the half-life t_1/2 (35 ℃) of M3 was prolonged by 4.8-time (from 17.8 min to 102.7 min), and the half deactivation temperature (T¹⁰₅₀) was increased from 38.1 ℃ to 40.3 ℃. The catalytic efficiencies toward pyruvate and 1-(R)-phenylethylamine of M3 were 1.59- and 1.56-fold that of WT. Molecular dynamics simulation and molecular docking showed that the reinforced stability of α-helix caused by the increase of hydrogen bond and hydrophobic interaction in molecules was the main reason for the improvement of enzyme thermostability. The enhanced hydrogen bond of substrate with surrounding amino acid residues and the enlarged substrate binding pocket contributed to the increased catalytic efficiency of M3. Substrate spectrum analysis revealed that the catalytic performance of M3 on 11 aromatic ketones were higher than that of WT, which further showed the application potential of M3 in the synthesis of chiral amines.
Transaminases/chemistry* ; Molecular Docking Simulation ; Amines/chemistry* ; Pyruvic Acid/metabolism* ; Enzyme Stability

Production of chiral amines and unnatural amino-acid using ω-transaminase can be achieved by kinetic resolution and asymmetric synthesis, thus ω-transaminase is of great importance in the synthesis of pharmaceutical intermediates. By genomic data mining, a putative ω-transaminase gene hbp was found in Burkholderia phytofirmans PsJN. The gene was cloned and over-expressed in Escherichia coli BL21 (DE3). The recombinant enzyme (HBP) was purified by Ni-NTA column and its catalytic properties and substrate profile were studied. HBP showed high relative activity (33.80 U/mg) and enantioselectivity toward β-phenylalanine (β-Phe). The optimal reaction temperature and pH were 40 ℃ and 8.0-8.5, respectively. We also established a simpler and more effective method to detect the deamination reaction of β-Phe by UV absorption method using microplate reader, and demonstrated the thermodynamic property of this reaction. The substrate profiling showed that HBP was specific to β-Phe and its derivatives as the amino donor. HBP catalyzed the resolution of rac-β-Phe and its derivatives, the products (R)-amino acids were obtained with about 50% conversions and 99% ee.
Bacterial Proteins ; biosynthesis ; genetics ; Burkholderia ; enzymology ; Cloning, Molecular ; Escherichia coli ; genetics ; metabolism ; Transaminases ; biosynthesis ; genetics

OBJECTIVETo retrospectively investigate the incidence of severe neutropenia and elevation of transaminase during neoadjuvant chemotherapy using epirubicin, cyclophosphamide and fluorouracil in breast cancer patients.

METHODSFrom January 2011 to December 2012, 303 consecutive breast cancer patients with complete treatment data treated in our department were included in this analysis. All patients received neoadjuvant chemotherapy with equal dose of EPI (100 mg/m(2)) administered every 3 weeks for 4 cycles before surgery.

RESULTS200 patients (66.0%) experienced at least one episode of grade 3/4 neutropenia/leukopenia, among them 176 patients experienced their first episode after the first cycle. Febrile neutropenia (FN) occurred in 13 patients for 14 episodes. Elevation of transaminase occurred in a total of 46 patients (15.2%), among them, grade 2 or higher elevation occurred in 15 patients (5.0%). Three blood test plans were adopted to monitor the patients during chemotherapy: (1) Routine blood count repeated every week; (2) Routine blood count before and on day 10 of each chemotherapy episode; (3) Routine blood count before and on day 7, 10 and 14 of each chemotherapy episode. The number of patients whose chemotherapy was delayed due to 3/4 neutropenia/leucopenia in each blood test plan was 3 (5.0%), 7 (3.9%) and 2 (3.2%), respectively. The number of patients with febrile neutropenia (FN) in each blood test plan was 2 (3.3%), 8 (4.4%) and 3 (4.8%), respectively. No statistically significant difference in treatment delay or the incidence of FN was observed among different blood test plans. No statistically significant difference in the incidence of grade 3/4 neutropenia/leukopenia or grade 2 or higher transaminase elevation was observed among different 5-Fu regimens.

CONCLUSIONSDuring neoadjuvant chemotherapy using FE100 C, Fci E100 C or E100 C for breast cancer patients without routine prophylactic G-CSF, the incidence of grade 3/4 neutropenia/leukopenia is 66.0%. With the patient management plan we adopted, 4.3% of patients developed febrile neutropenia. Prophylactic medication may not be necessary for patients without evident liver dysfunction.

Antineoplastic Combined Chemotherapy Protocols ; therapeutic use ; Breast Neoplasms ; drug therapy ; Cyclophosphamide ; therapeutic use ; Epirubicin ; therapeutic use ; Female ; Fluorouracil ; therapeutic use ; Granulocyte Colony-Stimulating Factor ; Humans ; Incidence ; Neoadjuvant Therapy ; Neutropenia ; metabolism ; Retrospective Studies ; Transaminases ; metabolism

The main causes of biliary obstruction are stones and cancers. Fascioliasis is a very rare case which causes biliary obstruction. Fascioliasis is a zoonosis caused by Fasciola hepatica which infects herbivores like sheep and cattle. F. hepatica lives in the biliary system or the liver parenchyma of a host. In Korea, the occurrence of this infection in human is very rare and only few cases have been reported. A 32-year-old male presented with upper abdominal pain and jaundice. His laboratory finding revealed elevated liver transaminases. Abdomen CT scan showed mild left intrahepatic bile duct dilatation. On ERCP, adult F. hepatica worms were found and were thus removed. Concurrently, clonorchiasis was diagnosed by stool exam and serologic enzyme-linked immunosorbent assay test. Clonorchiasis was treated with praziquantel. Herein, we report a case of intrahepatic bile duct dilatation due to F. hepatica infection with concurrent Clonorchis sinensis infestation.
Adult ; Animals ; Anthelmintics/therapeutic use ; Benzimidazoles/therapeutic use ; Bile Ducts, Intrahepatic ; Cholangiopancreatography, Endoscopic Retrograde ; Clonorchiasis/complications/*diagnosis/drug therapy ; Clonorchis sinensis/immunology/isolation & purification ; Enzyme-Linked Immunosorbent Assay ; Fasciola/isolation & purification ; Fascioliasis/complications/*diagnosis/parasitology ; Humans ; Liver/enzymology ; Male ; Praziquantel/therapeutic use ; Tomography, X-Ray Computed ; Transaminases/metabolism

Paracetamol (PCM) hepatotoxicity is related to reactive oxygen species (ROS) formation and excessive oxidative stress; natural antioxidant compounds have been tested as an alternative therapy. This study evaluated the hepatoprotective activity of an alcoholic extract of Boswellia ovalifoliolata (BO) bark against PCM-induced hepatotoxicity. BO extract also demonstrated antioxidant activity in vitro, as well as scavenger activity against 2, 2-diphenyl-1-picrylhydrazyl. Administration of PCM caused a significant increase in the release of transaminases, alkaline phosphatase, and lactate dehydrogenase in serum. Significant enhancement in hepatic lipid peroxidation and marked depletion in reduced glutathione were observed after parac intoxication with severe alterations in liver histology. BO treatment was able to mitigate hepatic damage induced by acute intoxication of PCM and showed a pronounced protective effect against lipid peroxidation, deviated serum enzymatic variables, and maintained glutathione status toward control. The results clearly demonstrate the hepatoprotective effect of BO against the toxicity induced by PCM.
Acetaminophen ; adverse effects ; Alkaline Phosphatase ; blood ; Animals ; Antioxidants ; metabolism ; pharmacology ; therapeutic use ; Biphenyl Compounds ; metabolism ; Boswellia ; Chemical and Drug Induced Liver Injury ; drug therapy ; metabolism ; pathology ; Glutathione ; metabolism ; L-Lactate Dehydrogenase ; blood ; Lipid Peroxidation ; drug effects ; Liver ; drug effects ; metabolism ; pathology ; Liver Function Tests ; Male ; Oxidative Stress ; drug effects ; Phytotherapy ; Picrates ; metabolism ; Plant Bark ; Plant Extracts ; pharmacology ; therapeutic use ; Rats, Wistar ; Transaminases ; blood

AIM: Nigella sativa L. (Ranunculaceae) is considered as a therapeutic plant-based medicine for liver damage. In this study, the aim was to study the effect of Nigella sativa oil (NSO) pretreatment on ethanol-induced hepatotoxicity in rats. METHOD: Rats were given Nigella sativa oil at doses of 2.5 and 5.0 mL·kg(-1), orally for 3 weeks, followed by oral ethanol (EtOH) administration (5 g·kg(-1)) every 12 h three times (binge model). RESULTS: Binge ethanol application caused significant increases in plasma transaminase activities and hepatic triglyceride and malondialdehyde (MDA) levels. It decreased hepatic glutathione (GSH) levels, but did not change vitamins E and vitamin C levels and antioxidant enzyme activities. NSO (5.0 mL·kg(-1)) pretreatment significantly decreased plasma transaminase activities, hepatic MDA, and triglyceride levels together with amelioration in hepatic histopathological findings. CONCLUSION NSO pretreatment may be effective in protecting oxidative stress-induced hepatotoxicity after ethanol administration.
Animals ; Disease Models, Animal ; Ethanol ; adverse effects ; Female ; Humans ; Liver ; drug effects ; injuries ; metabolism ; Liver Diseases, Alcoholic ; drug therapy ; enzymology ; etiology ; metabolism ; Malondialdehyde ; metabolism ; Nigella sativa ; chemistry ; Oxidative Stress ; drug effects ; Plant Oils ; administration & dosage ; Protective Agents ; administration & dosage ; Rats ; Rats, Sprague-Dawley ; Superoxide Dismutase ; metabolism ; Transaminases ; blood

Abrus mollis is a widely used traditional Chinese medicine for treating acute and chronic hepatitis, steatosis, and fibrosis. It was found that the total flavonoid C-glycosides from Abrus mollis extract (AME) showed potent antioxidant, anti-inflammatory, and hepatoprotective activities. To further investigate the hepatoprotective effect of AME and its possible mechanisms, lipopolysaccharide (LPS)-induced liver injury models were applied in the current study. The results indicated that AME significantly attenuated LPS-induced lipid accumulation in mouse primary hepatocytes as measured by triglyceride (TG) and total cholesterol (TC) assays and Oil Red O staining. Meanwhile, AME exerted a protective effect on LPS-induced liver injury as shown by decreased liver index, serum aminotransferase levels, and hepatic lipid accumulation. Real-time PCR and immunoblot data suggested that AME reversed the LPS-mediated lipid metabolism gene expression, such as sterol regulatory element-binding protein-1 (SREBP-1), fatty acid synthase (FAS), and acetyl-CoA carboxylase 1 (ACC1). In addition, LPS-induced overexpression of activating transcription factor 4 (ATF4), X-box-binding protein-1 (XBP-1), and C/EBP homologous protein (CHOP) were dramatically reversed by AME. Furthermore, AME also decreased the expression of LPS-enhanced interleukin-6 (IL-6) and cyclooxygenase-2 (COX-2). Here, it is demonstrated for the first time that AME ameliorated LPS-induced hepatic lipid accumulation and that this effect of AME can be attributed to its modulation of hepatic de novo fatty acid synthesis. This study also suggested that the hepatoprotective effect of AME may be related to its down-regulation of unfolded protein response (UPR) activation.
Abrus ; chemistry ; Animals ; Anti-Inflammatory Agents ; pharmacology ; therapeutic use ; Antioxidants ; pharmacology ; therapeutic use ; Chemical and Drug Induced Liver Injury ; drug therapy ; metabolism ; Cholesterol ; metabolism ; Down-Regulation ; Flavonoids ; pharmacology ; therapeutic use ; Glycosides ; pharmacology ; therapeutic use ; Hepatocytes ; drug effects ; metabolism ; Inflammation Mediators ; metabolism ; Lipid Metabolism ; drug effects ; Lipopolysaccharides ; Liver ; cytology ; drug effects ; metabolism ; Male ; Mice, Inbred Strains ; Phytotherapy ; Plant Extracts ; pharmacology ; therapeutic use ; Transaminases ; blood ; Triglycerides ; metabolism ; Unfolded Protein Response ; drug effects