Fat metabolism in higher plants

Abstract

Avocado [Persea americana] mesocarp extracts contain both acyl-CoA and acyl-acyl carrier protein (ACP) hydrolase [EC 3.1.2] activities. These activities were separated by a sequence of ammonium sulfate fractionations, DEAE-cellulose and hydroxyapatite column chromatography. Two distinct acyl-CoA hydrolase fractions and 1 acyl-ACP hydrolase fraction were obtaind. The acyl-ACP hydrolase fraction was essentially free of acyl-CoA hydrolase activity, had a pH optimum of 9.5 and a MW of 70-80,000 based on sucrose density gradient centrifugation and gel filtration chromatography. Substrate specificity studies showed that lauroyl-ACP, myristoyl-ACP, palmitoyl-ACP and stearoyl-ACP were slowly hydrolyzed but oleoyl-ACP was rapidly hydrolyzed to free fatty acid. These results suggest a possible role for acyl-ACP hydrolase as 1 component of a switching system which allows, indirectly, acyl transfer from ACP to CoA derivatives in plant cells.