Substrate stabilization of the palmitoyl-coenzyme A hydrolase activity of rat submaxillary gland

The long-chain acyl-CoA hydrolase (EC 3.1.2.2) activity of rat submaxillary salivary gland, found in the postmicrosomal supernatant fraction, has a pH optimum of 7.4. This hydrolase activity was found to be extremely labile, but inclusion of glycerol or the substrate palmitoyl-CoA in the preparations markedly stabilized the activity. Gel-filtration studies revealed multiple forms of the hydrolase, a lower-molecular-weight species of approx. 45 000 and a higher-molecular-weight species of approx. 130 000 observed when glycerol (20%, v/v) or palmitoyl-CoA (10 micro M) were included in the eluting buffer. This phenomenon is similar to that observed with the palmitoyl-CoA hydrolase of rat brain, except that there is no evidence that the higher-molecular-weight species of the hydrolase of submaxillary gland is generated by substrate-induced dimerization of the lower-molecular-weight species.