title: Pyridoxal 5' phosphate involvement in age-related modifications of tyrosine aminotransferase: multiple form patterns.
abstract: Multiple form patterns of tyrosine aminotransferase were studied in senescent and adult rat liver. Two main modifications were described for "old" rat enzyme: (i) appearance of a new molecular form, specific for old rats, eluted after adult form III and having other properties identical to this form; (ii) disappearance of intermediate forms II and III after enzyme induction; this result seems to be due to acceleration of the conversion process. Vitamin B6 deficiency of old rats explain this and other (previously described) post-translational modifications of "old" tyrosine aminotransferase. The influence of pyridoxal 5' phosphate and the role of protease(s) in the multiple form conversion are discussed. Moreover we show the possibility of a correlation between in vivo alterations of the enzyme molecule and modifications of tyrosine aminotransferase multiple form patterns observed in vitro.
mesh_terms: D000375:Aging; D000818:Animals; D003513:Cycloheximide / Q000494:pharmacology; D008099:Liver / Q000201:enzymology*; D011732:Pyridoxal Phosphate / Q000172:deficiency / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D014108:Tosylphenylalanyl Chloromethyl Ketone / Q000494:pharmacology; D014444:Tyrosine Transaminase / Q000378:metabolism*
chemical_list: D014108:Tosylphenylalanyl Chloromethyl Ketone; D011732:Pyridoxal Phosphate; D003513:Cycloheximide; D014444:Tyrosine Transaminase