Effect of acylation stimulating protein on the triacylglycerol synthetic pathway of human adipose tissue.

Acylation stimulating protein (ASP) is a 14 kDa plasma protein which causes in vitro triacylglycerol synthesis in human adipocytes and fibroblasts to increase substantially. ASP was found to stimulate human adipose tissue microsomal glycerophosphate acyltransferase and diacylglycerol acyltransferase activities by 23% and 90%, respectively. However, phosphatidate phosphohydrolase activity showed no increase in activity, nor did microsomal acyl-CoA synthetase activity. Moreover, ASP did not decrease the apparent Km of diacylglycerol acyltransferase (DGAT), but rather increased its apparent Vmax suggesting direct interaction of ASP with DGAT.