Solubilization of diglyceride acyltransferase from the membrane of Mycobacterium smegmatis

Diglyceride acyltransferase [acyl-CoA : 1,2-diacylglycerol O-acyltransferase, EC 2.3.1.20] was found to be localized in the membrane of Mycobacterium smegmatis, and this enzyme could be solubilized from the membrane by treatment with aqueous acetone. The solubilized enzyme required either 1,2-diolein or 1, 3-diolein as an acceptor for palmitoyl-CoA. The apparent Km value for 1,2- or 1,3-diolein and that for palmitoyl-CoA were about 1.4 X 10(-5) M and 6 X 10(-6) M, respectively. Several sulfhydryl reagents were inhibitory to the enzyme activity, suggesting the existence of a thiol group(s) in its active site. The solubilized enzyme, which was more labile than that membrane-bound one, could be stabilized to some extent with antichaotropic salts such as phosphate, pyrophosphate, and sulfate.