Pentalenolactone D synthase (, penE (gene), pntE (gene)) is an enzyme with systematic name 1-deoxy-11-oxopentalenate,NADH:oxygen oxidoreductase (pentalenolactone-D forming). It 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 pentalenolactone D, oxidised NADP<sup>+</sup>, and water. The starting ketone is made as part of the biosynthetic pathway to pentalenolactone in Streptomyces avermitilis.
The enzyme is a Baeyer-Villiger monooxygenase that uses flavin adenine dinucleotide as a cofactor.