In enzymology, lovastatin nonaketide synthase () is an enzyme that catalyzes the chemical reaction
The 5 substrates of this enzyme are acetyl-CoA, malonyl-CoA, NADPH, H<sup>+</sup>, and S-adenosyl-L-methionine, whereas its 6 products are dihydromonacolin L, CoA, CO<sub>2</sub>, NADP<sup>+</sup>, S-adenosyl-L-homocysteine, and H<sub>2</sub>O.
This enzyme belongs to the family of transferases, specifically those acyltransferases transferring groups other than aminoacyl groups. The systematic name of this enzyme class is acyl-CoA:malonyl-CoA C-acyltransferase (decarboxylating, oxoacyl- and enoyl-reducing, thioester-hydrolysing).