The enzyme, found in green sulfur bacteria (Chlorobiaceae), is a radical S-adenosyl-L-methionine (AdoMet) enzyme and contains a [4Fe-4S] cluster. It catalyses two consecutive hydroxylation reactions of the C-7 methyl group of bacteriochlorophyllide c to form a geminal diol intermediate that spontaneously dehydrates to produce the formyl group of bacteriochlorophyllide e.
a mutant lacking BciD exclusively gives bacteriochlorophyll-c, but not bacteriochlorophyll-e. The mutation drastically alters the homolog and epimer composition of the pigment. The methylation at the 82-position in the mutant cells proceeds to create bacteriochlorophyll-c carrying large alkyl substituents at this position. Correspondingly, the content of bacteriochlorophyll-c having the (S)-configuration at the chiral 31-position remarkably increases and accounts for 80.6% of the total bacteriochlorophyll-c. A new bacteriochlorophyll-c bearing the bulky triple 82-methylated neopentyl substituent at the 8-position is produced
bciD mutant cells are green in color, and accumulate bacteriochlorophyll-c homologs bearing the 7-methyl group, compared to C7-formylated bacteriochlorophyll-e homologs in the wild-type. In the mutant, (31S)-8-isobutyl-12-ethyl-bacteriochlorophyll-c is unusually predominant
Mizoguchi, T.; Harada, J.; Tsukatani, Y.; Tamiaki, H.
Isolation and characterization of a new bacteriochlorophyll-c bearing a neopentyl substituent at the 8-position from the bciD-deletion mutant of the brown-colored green sulfur bacterium Chlorobaculum limnaeum