A method for purifying acylation stimulating protein (ASP) from porcine serum is described. The mRNA encoding ASP was cloned by reverse transcriptase-polymerase chain reaction which predicted a 76 residue peptide. Based on this sequence, we generated antisera to a C-terminal peptide (ASP(1-20)) which aided ASP purification. Identity of the purified protein was verified by N-terminal sequencing. The molecular mass of porcine ASP is 8926. Porcine ASP stimulated esterification of fatty acid into triacylglycerol in cultured human cells with potency similar to that of human ASP (twofold at 5 muM). Based on this evidence that ASP exists in porcine blood, and that it has acylation stimulating activity, we propose that ASP may play a role in regulation of energy storage in adipose tissue in the pig. (C) 2002 Elsevier Science (USA). All rights reserved.