O-acetyltransferase; part of the gene cluster that mediates the biosynthesis of pyripyropene A, a specific human acyl-coenzyme A:cholesterol acyltransferase 2 inhibitor (PubMed:20861902). The first step of the pathway is the synthesis of nicotinyl-CoA from nicotinic acid by the nicotinic acid-CoA ligase pyr1 (PubMed:20861902). Nicotinyl-CoA is then a substrate of polyketide synthase pyr2 to produce 4-hydroxy-6-(3-pyridinyl)-2H-pyran-2-one (HPPO) which is further prenylated by the polyprenyl transferase pyr6 to yield farnesyl-HPPO (PubMed:20861902). The next steps consist of an epoxidation of farnesyl-HPPO to epoxyfarnesyl-HPPO by FAD-dependent monooxygenase pyr5 and a cyclization of the terpenoid portion by the terpene cyclase pyr4 to yield deacetyl-pyripyropene E (PubMed:20861902). The 2 cytochrome P450 monooxygenases pyr3 and pyr9, and the 2 acetyltransferases pyr7 and pyr8 are involved in the conversion of deacetyl-pyripyropene E into pyripyropene A through several cycles of oxidation and acetylation steps (PubMed:20861902). Pyr7 acetylates deacetyl-pyripyropene E to pyripyropene E which is oxidized to 11-deacetyl-pyripyropene O by pyr3, which is in turn acetylated into pyripyropene O by pyr8 (PubMed:21224862, PubMed:26019565). Pyripyropene O is then oxidized to deacetyl-pyripyropene A by pyr9 (PubMed:21224862). Deacetyl-pyripyropene A is finally acetylated to pyripyropene A by pyr8 (PubMed:26019565). Secondary metabolite biosynthesis; terpenoid biosynthesis. Pyripyropene A and its derivatives have very unique characteristics of selectively inhibiting the acyl-coenzyme A:cholesterol acyltransferase 2 (ACAT2) isozyme (PubMed:18997389). Therefore, pyripyropenes are expected to be developed as a new type of anti-atherosclerotic agent (PubMed:18997389). Furthermore, pyripyropenes have been shown to exhibit anti-angiogenic activity against human umbilical vein endothelial cells (PubMed:19571395). Finally, pyripyropene A also exhibits insecticidal properties (PubMed:8534106). Belongs to the fumigaclavine B O-acetyltransferase family.