Tyrosine aminotransferase in AKR/J albino and C57BL/6J black mouse skin.
L-Tyrosine aminotransferase is present in a high speed supernatant fraction of skin homogenate of AKR/J albino and C57BL/6J black mice. The conversion of tyrosine to p-hydroxyphenylpyruvate was shown to be catalyzed by an aminotransferase by the following observations: the reaction was partially dependent on the presence of low concentrations of alpha-ketoglutarate; catalase was ineffective in increasing the yield of p-hydroxyphenylpyruvate; there was potent inhibition by typical inhibitors of pyridoxal phosphate enzymes and of rat liver tyrosine aminotransferase; there was no inhibition by inhibitors of L-amino acid oxidase; and there was no oxidation of L-leucine, the best substrate for rat kidney L-amino acid oxidase. The aminotransferase was stimulated by mercaptoethanol and was inhibited by high concentrations of alpha-ketoglutarate. The apparent Km for tyrosine was 5 X 10(-3) M and the molecular weight, determined by sucrose density gradient centrifugation, was 150-200,000. Dopa was also transaminated by the crude enzyme. No tyrosine aminotransferase could be detected in extracts of hamster melanoma.
D000594:Amino Acid Oxidoreductases / Q000378:metabolism; D000818:Animals; D006224:Cricetinae; D066298:In Vitro Techniques; D007700:Kinetics; D007980:Levodopa / Q000378:metabolism; D008545:Melanoma / Q000201:enzymology; D051379:Mice; D008806:Mice, Inbred AKR; D008810:Mice, Inbred C57BL; D008970:Molecular Weight; D010667:Phenylpyruvic Acids / Q000378:metabolism; D010858:Pigmentation; D012867:Skin / Q000201:enzymology*; D013045:Species Specificity; D013379:Substrate Specificity; D014444:Tyrosine Transaminase / Q000378:metabolism*
D010667:Phenylpyruvic Acids; D007980:Levodopa; D000594:Amino Acid Oxidoreductases; D014444:Tyrosine Transaminase