Analysis of Pigments in Cyanobacteria Synechocystis sp. PCC6803 that Express BchF, 3-Vinyl Bacteriochlorophyllide Hydratase, from Purple Bacteria Rhodobacter capsulatus

Abstract

Chl a is synthesized from chlorophyllide (Chlide) a by esterification of long alcohol chains to its side-chain of ring D, while, BChl a is synthesized from bacteriochlorophyllide a. To convert Chlide a to bacteriochlorophyllide a, two reactions, the reduction of the double bond of ring B and the oxidation of the C3 vinyl group, are necessary. A 3-vinyl bacteriochlorophyllide hydratase which is encoded on bchF gene is seemed to be involved in the latter reaction. We introduced a gene of 3-vinyl bacteriochlorophyllide hydratase, bchF, from purple bacteria Rhodobacter capsulatus into cyanobacteria Synechocystis sp. PCC6803. HPLC analysis revealed that 4 kinds of polar Chl derivatives which are not observed in wild type cells are presented in Synechocystis sp. PCC6803 that express BchF. The absorption spectra of these pigments are very similar and FAB-mass analysis indicated all of the pigments have a same mass-number, suggested these are 3-hydroxyethyl-chlorophyllide a and its stereoisomers.