On the mechanism of inactivation and ATP-dependent reactivation of rat liver tyrosine aminotransferase.
The mechanism of in vitro inactivation and ATP-dependent rapid reactivation of rat liver tyrosine aminotransferase by a membrane-bound system from rat liver and kidney cortex and the nucleotide specificity of this process was investigated using partially purified tyrosine amino-transferase as a substrate. Adenosine 5'-triphosphate (ATP) could be replaced by guanosine 5'-triphosphate (GTP), Whereas inosine 5'-triphosphate (ITP) was less effective. During reactivation [gamma-32P]ATP was incorporated into the enzyme and not excorporated by incubation of the labeled enzyme with excess non-radioative ATP. Inactivation of labeled tyrosine aminotransferase by a particulate fraction led to a decrease protein-bound radioactivity concomitant with an increase of [32P]orthophosphate. This points to a phosphorylation and dephosphorylation mechanism in the regulation of tyrosine aminotransferase activity.
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D004789:Enzyme Activation / Q000187:drug effects; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D011732:Pyridoxal Phosphate / Q000494:pharmacology; D051381:Rats; D013347:Subcellular Fractions / Q000201:enzymology; D014444:Tyrosine Transaminase / Q000302:isolation & purification / Q000378:metabolism*
D011732:Pyridoxal Phosphate; D000255:Adenosine Triphosphate; D014444:Tyrosine Transaminase; D008274:Magnesium