6] Glycerophosphate acyltransferase from liver

Abstract

Publisher Summary In mammalian organs, glycerophosphate acyltranferase is present in both the endoplasmic reticulum (microsomes) and mitochondrial outer membrane. In liver, the glycerophosphate acyltransferase activity is nearly equal in these two organelles, whereas in other organs the microsomal acyltransferase is approximately 10 times more active than the mitochondrial enzyme. The enzyme activity can be measured by following the conversion of sn -[2- 3 H]glycerol 3-phosphate to l-butanol-extractable lipid. The liver microsomal glycerophosphate acyltransferase is inhibited by all proteases. The mitochondrial enzyme, on the other hand, is not inhibited by trypsin and chymotrypsin. Non-site-specific proteases, such as proteinase K and subtilisin, inhibit the mitochondrial enzyme. The degree of inhibition increases if the ionic strength of the incubation medium is lowered. Both microsomal and mitochondrial glycerophosphate acyltransferase have been only partially purified. In contrast, the Escherichia coli glycerophosphate acyltranferase has been completely purified, its properties studied, and the gene cloned and sequenced. The successful purification of the prokaryotic enzyme has been facilitated by massive overproduction of the enzyme owing to molecular cloning.