title: Purification and characterization of a tyrosine aminotransferase from Crithidia fasciculata.
abstract: Tyrosine aminotransferase (TAT, EC 2.6.1.5) from the kinetoplastid, Crithidia fasciculata, was purified over 2000 fold to electrophoretic homogeneity. The native form of the enzyme had a molecular weight of approximately 100,000, whereas under denaturing conditions it produced two polypeptides of approximately 50,000 and 48,000, respectively. Absence of a reaction with the periodic acid-Schiff stain suggested that the crithidial enzyme was not a glycoprotein. It was relatively stable and remained active over a wide range of pH and temperature. It exhibited a broad substrate specificity and was able to utilize L-tyrosine, L-tryptophan, and L-phenylalanine as amino donors. Antiserum produced against partially purified crithidial tyrosine aminotransferase failed to inhibit the enzymatic activity. The same antiserum cross-reacted with a soluble extract from Trypanosoma brucei gambiense, but not with that from normal mouse liver, confirming evolutionary conservatism between the two protozoa.
mesh_terms: D000818:Animals; D002845:Chromatography; D003421:Crithidia / Q000201:enzymology*; D003429:Cross Reactions; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D051379:Mice; D010649:Phenylalanine / Q000378:metabolism; D013379:Substrate Specificity; D013696:Temperature; D014347:Trypanosoma brucei gambiense / Q000276:immunology; D014364:Tryptophan / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism; D014444:Tyrosine Transaminase / Q000032:analysis / Q000276:immunology / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D014443:Tyrosine; D010649:Phenylalanine; D014364:Tryptophan; D014444:Tyrosine Transaminase