ISOLATION AND CHARACTERIZATION OF MITOCHONDRIAL ACYL-COA - GLYCINE N-ACYLTRANSFERASES FROM KIDNEY

When bovine kidney mitochondria were assayed in the presence of Triton X-100, they were found to contain glycine N-acyltransferase activity toward the CoA-adducts of benzoate, butyrate, isovalerate, naphthylace tate, phenylacetate, and salicylate. Heptanoyl-CoA activity was masked by high acyl-CoA hydrolase activity. All activities found in detergen t-lysed mitochondria, and also that toward heptanoyl-CoA, could be rel eased in soluble form by repeated cycles of freeze-thawing. Activity i n the particle-free lysate decreased in the order: phenylacetyl-CoA > benzoyl-CoA > salicylyl-CoA > butyryl-CoA > naphthylacetyl-CoA > hepta noyl-CoA > isovaleryl-CoA. This is quite different from liver, where t he activity toward the arylacetic acids is much lower and the other ac tivities are higher. This reflects a major difference in the relative expression of the aralkyl and arylacetyl transferases between liver an d kidney. The phenylacetyl-CoA and naphthylacetyl-CoA activity purifie d with a single protein which is termed the arylacetyl transferase. Th is enzyme was similar to the hepatic arylacetyl transferase in terms o f its sensitivity to sulfhydryl reagents, response to cations, and mol ecular weight (33,500). Activity toward benzoyl-CoA also purified as a single form which was similar to the hepatic form in its molecular we ight (34,000), response to cations, and kinetic properties. Conditions leading to the inhibition of this kidney form and also the hepatic fo rm by p-mercuribenzoate are described.