title: In Vitro Assays of BciC Showing C132-Demethoxycarbonylase Activity Requisite for Biosynthesis of Chlorosomal Chlorophyll Pigments.
abstract: A BciC enzyme is related to the removal of the C13(2)-methoxycarbonyl group in biosynthesis of bacteriochlorophylls (BChls) c, d and e functioning in green sulfur bacteria, filamentous anoxygenic phototrophs and phototrophic acidobacteria. These photosynthetic bacteria have the largest and the most efficient light-harvesting antenna systems, called chlorosomes, containing unique self-aggregates of BChl c, d or e pigments, that lack the C13(2)-methoxycarbonyl group which disturbs chlorosomal self-aggregation. In this study, we characterized the BciC derived from the green sulfur bacterium Chlorobaculum tepidum, and examined the in vitro enzymatic activities of its recombinant protein. The BciC-catalyzing reactions of various substrates showed that the enzyme recognized chlorophyllide (Chlide) a and 3,8-divinyl(DV)-Chlide a as chlorin substrates to give 3-vinyl-bacteriochlorophyllide (3V-BChlide) d and DV-BChlide d, respectively. Since the BciC afforded a higher activity with Chlide a than that with DV-Chlide a and no activity with (DV-)protoChlides a (porphyrin substrates) and 3V-BChlide a (a bacteriochlorin substrate), this enzyme was effective for diverting the chlorosomal pigment biosynthetic pathway at the stage of Chlide a away from syntheses of other pigments such as BChl a and Chl a The addition of methanol to the reaction mixture did not prevent the BciC activity, and we identified this enzyme as Chlide a demethoxycarbonylase, not methylesterase.
authors.affiliation: Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, 525-8577 Japan.
authors.forename: Misato
authors.initials: M
authors.lastname: Teramura
authors.affiliation: Department of Medical Biochemistry, Kurume University School of Medicine, Kurume, Fukuoka, 830-0011 Japan jiro_harada@med.kurume-u.ac.jp tamiaki@fc.ritsumei.ac.jp.
authors.forename: Jiro
authors.initials: J
authors.lastname: Harada
authors.affiliation: Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, 525-8577 Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Mizoguchi
authors.affiliation: Department of Medical Biochemistry, Kurume University School of Medicine, Kurume, Fukuoka, 830-0011 Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Yamamoto
authors.affiliation: Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, 525-8577 Japan jiro_harada@med.kurume-u.ac.jp tamiaki@fc.ritsumei.ac.jp.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Tamiaki
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001429:Bacteriochlorophylls / Q000235:genetics / Q000378:metabolism*; D053898:Biosynthetic Pathways; D019414:Chlorobi / Q000201:enzymology* / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D000432:Methanol; D015388:Organelles / Q000378:metabolism; D010858:Pigmentation; D011994:Recombinant Proteins; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; D011994:Recombinant Proteins; C002084:bacteriochlorophyll c; D000432:Methanol
keywords: Bacteriochlorophyll; BciC; Chlorosome; Green sulfur bacteria; Photosynthetic bacteria