Child, Preschool ; Female ; Humans ; Infant ; Male ; Methionine ; blood ; Tyrosine ; blood ; Tyrosine Transaminase ; deficiency ; Tyrosinemias ; blood ; diagnosis ; enzymology ; pathology ; therapy

Tyrosine aminotransferase (TAT) catalyzes the transamination of tyrosine and other aromatic amino acids. The enzyme is thought to play a role in tyrosinemia type II, hepatitis and hepatic carcinoma recovery. The objective of this study is to investigate its biochemical and structural characteristics and substrate specificity in order to provide insight regarding its involvement in these diseases. Mouse TAT (mTAT) was cloned from a mouse cDNA library, and its recombinant protein was produced using Escherichia coli cells and purified using various chromatographic techniques. The recombinant mTAT is able to catalyze the transamination of tyrosine using α-ketoglutaric acid as an amino group acceptor at neutral pH. The enzyme also can use glutamate and phenylalanine as amino group donors and p-hydroxy-phenylpyruvate, phenylpyruvate and alpha-ketocaproic acid as amino group acceptors. Through macromolecular crystallography we have determined the mTAT crystal structure at 2.9 Å resolution. The crystal structure revealed the interaction between the pyridoxal-5'-phosphate cofactor and the enzyme, as well as the formation of a disulphide bond. The detection of disulphide bond provides some rational explanation regarding previously observed TAT inactivation under oxidative conditions and reactivation of the inactive TAT in the presence of a reducing agent. Molecular dynamics simulations using the crystal structures of Trypanosoma cruzi TAT and human TAT provided further insight regarding the substrate-enzyme interactions and substrate specificity. The biochemical and structural properties of TAT and the binding of its cofactor and the substrate may help in elucidation of the mechanism of TAT inhibition and activation.
Animals ; Catalytic Domain ; Crystallography, X-Ray ; Humans ; Mice ; Molecular Dynamics Simulation ; Tyrosine Transaminase ; chemistry

PURPOSE: Primary mammalian hepatocytes largely retain their liver-specific functions when they are freshly derived from donors. However, long-term cultures of functional hepatocytes are difficult to establish. To increase the longevity and maintain the differentiated functions of hepatocytes in primary culture, cells can be cultured in a sandwich configuration of collagen. In such a configuration, hepatocytes can be cultured for longer periods compared with cultures on single layers of collagen. However, research regarding mouse hepatocytes in sandwich culture is lacking. METHODS: Primary mouse hepatocytes were sandwiched between two layers of collagen to maintain the stability of their liver-specific functions. After gelation, 2 mL of hepatocyte culture medium was applied. RESULTS: After 24 hours, 5, 10 days of culture, the collagen gel sandwich maintained the cellular border and numbers of bile canaliculi more efficiently than a single collagen coating in both high and low density culture dishes. Reverse transcription-polymerase chain reaction analysis of alpha-1-antitrypsin (AAT), hepatocyte nuclear factor 4 alpha (HNF4A), alphafetoprotein, albumin, tryptophan oxygenase (TO), the tyrosine aminotransferase gene, glucose-6-phosphatase, glyceraldehyde-3-phosphate dehydrogenase for mouse primary hepatocytes cultured on collagen coated dishes and collagen gels showed superior hepatocyte-related gene expression in cells grown using the collagen gel sandwich culture system. AAT, HNF4A, albumin, TO were found to be expressed in mouse hepatocytes cultured on collagen gels for 5 and 10 days. In contrast, mouse hepatocytes grown on collagen-coated dishes did not express these genes after 5 and 10 days of culture. CONCLUSION: The collagen gel sandwich method is suitable for primary culture system of adult mouse hepatocytes.
Adult ; Animals ; Bile Canaliculi ; Collagen ; Gels ; Gene Expression ; Glucose-6-Phosphatase ; Hepatocyte Nuclear Factor 4 ; Hepatocytes ; Humans ; Longevity ; Mice ; Oxidoreductases ; Tissue Donors ; Tryptophan Oxygenase ; Tyrosine Transaminase

We studied the influence of the concentration of Ca2+ (0-50 mmol/L) in culture medium on the synthesis of rosmarinic acid (RA) and related enzymes in Salvia miltiorrhiza suspension cultures. Using verpamil (VP, a calcium channel antagonist) and ionophore A23187, we studied the mechanism of secondary metabolites of Salvia miltiorrhiza suspension cultures influenced by the concentration of Ca2+ in the culture medium. The synthesis of intracellular RA in 6-day incubation was significantly dependent on the medium Ca2+ concentration. At the optimal Ca2+ concentration of 10 mmol/L, a maximal RA content of 20.149 mg/g biomass dry weight was reached, which was about 37.3% and 20.4% higher than that at Ca2+ concentrations of 1 and 3 mmol/L, respectively. The variation of the activity of PAL and TAT, two key enzymes of the two branches of RA, could be affected by the concentration of Ca2+ in culture medium. The change of their activity occurred prior to the accumulation of RA, which suggested both of the key enzymes be involved in the synthesis of RA. Meanwhile, the enzymatic action of PAL was more distinct than TAT. The treatment of VP and A23187, respectively, indicated that the influence of RA affected by the concentration of Ca2+ in the culture medium was accomplished by the intracellular Ca2+, and the flow of Ca2+ from the extracellular to the intracellular environment could also participate in this process.
Calcium ; pharmacology ; Cinnamates ; metabolism ; Culture Media ; Culture Techniques ; methods ; Depsides ; metabolism ; Phenylalanine Ammonia-Lyase ; metabolism ; Salvia miltiorrhiza ; chemistry ; enzymology ; growth & development ; Tyrosine Transaminase ; metabolism

To investigate roles of nitric oxide (NO) signal in accumulations of phenolic acids in abscisic.acid (ABA)-induced Salvia miltiorrhiza hairy roots, S. miltiorrhiza hairy roots were treated with different concentrations of sodium nitroprusside (SNP)-an exogenous NO donor, for 6 days, and contents of phenolic acids in the hairy roots are determined. Then with treatment of ABA and NO scavenger (2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethylimidazoline-1- oxyl-3-oxide, c-PTIO) or NO synthase inhibitor (NG-nitro-L-arginine methyl ester, L-NAME), contents of phenolic acids and expression levels of three key genes involved in phenolic acids biosynthesis were detected. Phenolic acids production in S. miltiorrhiza hairy roots was most significantly improved by 100 µmoL/L SNP. Contents of RA and salvianolic acid B increased by 3 and 4 folds. ABA significantly improved transcript levels of PAL (phenylalanine ammonia lyase), TAT (tyrosine aminotransferase) and RAS (rosmarinic acid synthase), and increased phenolic acids accumulations. However, with treatments of ABA+c-PTIO or ABA+L-NAME, accumulations of phenolic acids and expression levels of the three key genes were significantly inhibited. Both NO and ABA can increase accumulations of phenolic acids in S. miltiorrhiza hairy roots. NO signal probably mediates the ABA-induced phenolic acids production.
Abscisic Acid ; pharmacology ; Benzofurans ; metabolism ; Free Radical Scavengers ; pharmacology ; Hydroxybenzoates ; metabolism ; Nitric Oxide ; metabolism ; Phenylalanine Ammonia-Lyase ; metabolism ; Plant Roots ; metabolism ; Salvia miltiorrhiza ; metabolism ; Tyrosine Transaminase ; metabolism

Rosmarinic acid (RA), a phenolic acid, is one of the important secondary metabolites produced in Salvia miltiorrhiza. To observe the influence of salicylic acid (SA), an elicitor, on the synthesis of RA and related enzymes, we treated the cell suspension cultures of S. miltiorrhiza with SA and L-a-aminooxy-beta-phenylpropionic acid (AOPP), a competitive inhibitor of tyrosine aminotransferase (TAT). Under this condition, the activities of related enzymes, such as phenylalanine ammonia-lyase and TAT were traced and assayed; the accumulative amount of RA was measured. The results showed that the PAL activity reached the peak at 4 h, 124% higher than that of the control, and the content of RA reached its maximum ((5.914 +/- 0.296) mg/g dry weight) at 8 h, after treated by 6.25 mg/L SA on day 6 of the suspension culture. The results of treatment with 0.1 micromol/L AOPP showed that AOPP affected little on the TAT activity, while the PAL activity was significantly influenced, with 44% lower than that of the control at 6 h. Meanwhile, the reduced accumulation of RA ((4.709 +/- 0.204) mg/g dry weight) paralleled with the decrease in PAL activity. The co-treatment by 0.1 micromol/L AOPP and 6.25 mg/L SA relieved the restriction imposed by AOPP on PAL, and made the cell cultures accumulate more RA than sole treatment with AOPP, indicated that SA induced the accumulation of RA in suspension cell culture of S. miltiorrhiza, and the rate-limiting effect of PAL was stronger than TAT.
Cell Culture Techniques ; methods ; Cinnamates ; metabolism ; Depsides ; metabolism ; Phenylalanine Ammonia-Lyase ; metabolism ; Plant Cells ; metabolism ; Salicylic Acid ; pharmacology ; Salvia miltiorrhiza ; cytology ; growth & development ; metabolism ; Suspensions ; Tyrosine Transaminase ; metabolism

OBJECTIVETo study the mechanism by which AG490 improves the survival rate of rats following extensive liver resection.

METHODSThirty-eight rats were randomly divided into two groups after surgery: control group (n=10), without treatment; (2) AG490 group (n=28), with AG490 (1 mg x kg(-1) x 12 h(-1)) administrated intraperitoneally immediately and 36 hours after the operation. The survival rate was observed and the serum liver functions were measured.

RESULTSThe survival rates of control group and AG490 group were 0% and 25%. AG490 group had significantly better blood glucose and aminotransferase levels (P < 0.05) than control group; serum bilirubin levels significantly decreased 48 hours after the operation. Serum protein levels in both two groups had slow decrease but without statistical significance (P > 0.05).

CONCLUSIONSAG490 can significantly increase the survival rate of rats following extensive liver resection. Such a benefit mainly results from the protection towards residual liver function rather than from the promotion of liver regeneration.

Alanine Transaminase ; blood ; Animals ; Aspartate Aminotransferases ; blood ; Bilirubin ; blood ; Blood Glucose ; metabolism ; Enzyme Inhibitors ; pharmacology ; Hepatectomy ; methods ; Male ; Protein-Tyrosine Kinases ; antagonists & inhibitors ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Survival Rate ; Tyrphostins ; pharmacology

OBJECTIVETo study the function of ABA and fluridone on the contents of penolic acids and two key synthetases (PAL and TAT).

METHODConducted 4 different concentrations in the hairy root of Salvia miltiorrhiza after culturing 18 days and treated with fluridone. One day later, harvested the hairy root and measured the activity of PAL and TAT; Treatment for 6 days, gathered and determined the contents of phenolic acids.

RESULTIn certain concentration of ABA, lower ABA could induced the production of growth and higher ABA inhibitor the growth in hairy roots of S. miltiorrhiza; ABA induced the accumulation of caffeic acid considerably, and the effect on the contents of coffee acid show positive correlation; As for the RA and LAB, the low dosage of ABA simulated the production and higher ABA inhibited the production of them; the ABA biosynthetic inhibitor fluridone can decreases ABA's the effect; The different of ABA activated the activity of PAL and TAT, but the impact were discriminating, when treatment with ABA and fluridone, the inducing were declined.

CONCLUSIONABA induced the accumulation of.

Abscisic Acid ; antagonists & inhibitors ; metabolism ; pharmacology ; Antioxidants ; analysis ; metabolism ; Biomass ; Caffeic Acids ; analysis ; metabolism ; Herbicides ; pharmacology ; Hydroxybenzoates ; analysis ; metabolism ; Medicine, Chinese Traditional ; Phenylalanine Ammonia-Lyase ; drug effects ; metabolism ; Plant Roots ; drug effects ; enzymology ; growth & development ; Pyridones ; pharmacology ; Salvia miltiorrhiza ; drug effects ; enzymology ; growth & development ; Time Factors ; Tyrosine Transaminase ; drug effects ; metabolism