SUBSTRATE SPECIFICITIES OF GLYCEROL ACYLATING ENZYMES FROM DEVELOPING EMBRYOS OF 2 CUPHEA SPECIES

Embryos of Cuphea procumbens accumulate triacylglycerols with nearly 90 mol% of capric acid (10:0), whereas, C. wrightii embryo shave 33% of 10:0 and 54% of lauric acid (12:0) in their triacylglycerols. Acylation rates of different acyl substrates by microsomal glycerol 3-phosphate acyltransferases (GPAT, EC 2.3.1.15) and lysophosphatidic acid acyltransferases (LPAAT, EC 2.3.1.5 1), prepared from developing embryos of these species, were studied. Both types of enzymes differed in their acyl specificities between the two species. The GPAT and LPAAT from C. wrightii showed low activity with 10:0-CoA whereas this acyl-CoA was efficiently used for both acylation reactions by the C. procumbens enzymes. The LPAAT from C. wrightii showed relatively higher activities using acyl-CoA, with acyl chains longer than 10:0, than the corresponding enzyme from C. procumbens. With increasing chain length of the lysophosphatidic substrate increasingly longer acyl-CoA could serve as acyl donors in the LPAAT catalysed reaction from both species.