title: Binding of nucleotides to an extramitochondrial acetyl-CoA hydrolase from rat liver.
abstract: Cold labile extramitochondrial acetyl-CoA hydrolase (dimeric form) purified from rat liver was activated by various nucleoside triphosphates and inhibited by various nucleoside diphosphates. Activation of acetyl-CoA hydrolase by ATP was inhibited by a low concentration of ADP (Ki congruent to 6.8 microM) or a high concentration of AMP (Ki congruent to 2.3 mM). ADP and AMP were competitive inhibitors of ATP. A Scatchard plot of the binding of ATP to acetyl-CoA hydrolase (dimer) at room temperature gave a value of 25 microM for the dissociation constant with at least 2 binding sites/mol of dimer. Cold-treated monomeric enzyme also associated with ATP-agarose, suggesting that the monomeric form of the enzyme also has a nucleotide binding site(s), probably at least 1 binding site/mol of monomer. Phenylglyoxal or 2,3-butanedione, both of which modify arginyl residues of protein, inactivated acetyl-CoA hydrolase. ATP (an activator) greatly protected acetyl-CoA hydrolase from inactivation by these reagents, while ADP (an inhibitor) greatly (a substratelike, competitive inhibitor), and CoASH (a product) were less effective. However, addition of ADP plus valeryl-CoA (or CoASH) effectively prevented the inactivation by 2,3-butanedione, but that is not the case for phenylglyoxal. These results suggest that one or more arginyl residues are involved in the nucleotide binding site of extramitochondrial acetyl-CoA hydrolase and that their nucleotide binding sites locate near the substrate binding site.
mesh_terms: D000104:Acetyl-CoA Hydrolase / Q000302:isolation & purification / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000378:metabolism*; D000249:Adenosine Monophosphate / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008297:Male; D011485:Protein Binding; D051381:Rats; D011919:Rats, Inbred Strains; D013869:Thiolester Hydrolases / Q000378:metabolism*
chemical_list: D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D013869:Thiolester Hydrolases; D000104:Acetyl-CoA Hydrolase