The appearance of a new aromatic aminotransferase in the small intestines of vitamin B6-deficient rats.
Vitamin B6 deficiency led to a decrease in aspartate: 2-oxoglutarate aminotransferase activity and to a marked increase in phenylalanine:2-oxoglutarate aminotransferase activity in rat small intestines. The increased phenylalanine aminotransferase activity was found to be due to a newly appeared aromatic aminotransferase without the aspartate aminotransferase activity in the cytosol of the small intestinal mucosa. The enzyme preparation had an isoelectric point of pH 8.5, a pH optimum near 8.0, and a molecular weight of approximately 100,000 with two identical subunits. The enzyme showed aminotransferase activities towards various aromatic L-amino acids with 2-oxoglutarate as the amino acceptor. The order of effectiveness of aromatic L-amino acids was phenylalanine > tryptophan > tyrosine > 5-hydroxytryptophan; very little activity was detected with other L-amino acids that were tested. The enzyme was specific for 2-oxoglutarate as the amino acceptor. The enzyme was not detected in other tissues (liver, kidney, heart, and brain) from both control and vitamin B6-deficient rats. The enzyme has never been described before in animal tissues.
D000818:Animals; D001219:Aspartate Aminotransferases / Q000378:metabolism; D001835:Body Weight; D007421:Intestine, Small / Q000201:enzymology*; D046911:Macromolecular Substances; D008297:Male; D008970:Molecular Weight; D010649:Phenylalanine / Q000302:isolation & purification / Q000378:metabolism; D051381:Rats; D013379:Substrate Specificity; D000637:Transaminases / Q000302:isolation & purification / Q000378:metabolism*; D026681:Vitamin B 6 Deficiency / Q000201:enzymology*
D046911:Macromolecular Substances; D010649:Phenylalanine; D000637:Transaminases; C022340:phenylalanine aminotransferase; D001219:Aspartate Aminotransferases