Neopentalenolactone D synthase (, ptlE (gene)) is an enzyme with systematic name 1-deoxy-11-oxopentalenate,NADH:oxygen oxidoreductase (neopentalenolactone-D forming). This enzyme catalyses the following chemical reaction
The four substrates of this enzyme are 1-deoxy-11-oxopentalenic acid, reduced nicotinamide adenine dinucleotide phosphate (NADPH), oxygen, and a proton. It products are neopentalenolactone D, oxidised NADP<sup>+</sup>, and water. The starting ketone is made as part of a biosynthetic pathway in Streptomyces avermitilis which leads to pentalenolactone and related compounds.
The enzyme is a Baeyer-Villiger monooxygenase that uses flavin adenine dinucleotide as a cofactor.