Detection of 13-carboxy-chlorin produced by the in vitro BciC enzymatic hydrolysis of zinc chlorophyllide.

Green photosynthetic bacteria with an efficient light-harvesting system contain special chlorophyll molecules, called bacteriochlorophylls c, d, e, in their main antennae. In the biosynthetic pathway, a BciC enzyme is proposed to catalyze the hydrolysis of the C13-methoxycarbonyl group of chlorophyllide a, but the resulting C13-carboxy group has not been detected yet because it is spontaneously removed due to the instability of the β-keto-carboxylic acid. In this study, the in vitro BciC enzymatic reactions of zinc methyl (13R/S)-hydroxy-mesochlorophyllides a were examined and a carboxylic acid possessing the C13S-OH was first observed as the hydrolyzed product of the C13-COOCH.