Detection of 132-carboxy-chlorin produced by the in vitro BciC enzymatic hydrolysis of zinc chlorophyllide

[Display omitted] •Zinc methyl mesochlorophyllide a bearing the (131S)-hydroxy group was prepared.•A recombinant BciC protein catalytically hydrolyzed the (132R)-methoxycarbonyl group.•The 132-carboxy-chlorin was first observed as the hydrolyzed product.•The BciC enzyme functions as a hydratase both in vivo and in vitro.•The in vivo resulting β-keto-carboxylic acid is non-enzymatically decarboxylated. 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 C132-methoxycarbonyl group of chlorophyllide a, but the resulting C132-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 (131R/S)-hydroxy-mesochlorophyllides a were examined and a carboxylic acid possessing the C132S-OH was first observed as the hydrolyzed product of the C132-COOCH3.