Structural determination of dihydro‐ and tetrahydrogeranylgeranyl groups at the 17‐propionate of bacteriochlorophylls‐a

Abstract

In the final stage of bacteriochlorophyll (BChl) biosynthesis, the presence of BChl-a molecules possessing dihydrogeranylgeranyl and tetrahydrogeranylgeranyl groups at the 17-propionate has been reported. However, the molecular structures of such BChls-a have not yet been determined in terms of the positions of C‚C double bonds in the 17 2 -ester. In this study, we isolated significant amounts of such pure BChls-a from Rhodopseudomonas palustris and determined their structures by both mass spectrometry and 1 H and 13 C NMR spectroscopy. The determined structures enable us to discuss a stepwise reduction from a geranylgeranyl to phytyl substituent.

Chlorophyllide a Oxidoreductase Works as One of the Divinyl Reductases Specifically Involved in Bacteriochlorophyll a Biosynthesis

“…Although BciA and BciB are not indispensable for BChl a biosynthesis, as shown in this study, the two enzymes are required for biosynthesis of ⌬2,6-phytadienylated Chl a and BChl c/d/e. In our previous study, the bciA mutant of C. tepidum synthesized normal BChl a but accumulated 8-vinyl-⌬2,6-phytadienylated Chl a and 8V-BChl c (26). This suggests that COR would not release Chlide a after the 8-vinyl reduction of 8V-Chlide a and then would immediately proceed to the C7ϭC8 double bond reduction for further BChl a biosynthesis.…”

“…R. sphaeroides J001 and R. palustris J002 strains were rifampicin-resistant derivatives from R. sphaeroides 2.4.1 (26) and R. palustris CGA009 (27), respectively, and used as wild type strains in this study. These bacteria were grown in liquid or on solid PYS media (27) at 30°C under aerobically and semiaerobically dark conditions for genetic manipulations and pigment analyses, respectively, or anaerobi- cally illuminated conditions for phototrophic growth.…”

“…These peaks were assigned to BChls a carrying a geranylgeranyl (peak 2), dihydrogeranylgeranyl (peak 3), or tetrahydrogeranylgeranyl group (peak 4) in the 17-propionate residues in the order of elution. The assignment of these three BChl a components was established in our previous studies (26,27). The function of BciB could not be clarified using the dB strain, as in the situation of BciA using the dA strain.…”

Reduction Processes in Biosynthesis of Chlorophyll Molecules: Chemical Implication of Enzymatically Regio- and Stereoselective Hydrogenations in the Late Stages of Their Biosynthetic Pathway

“…62,63 From the cultured cells of one of the above strains, each pigment was separated by HPLC and analyzed by 1 H/ 13 C NMR spectroscopy. 64 The four isolated species were confirmed and their molecular structures were identified. The dihydro-and tetrahydrogenated species had 6,7-DHGG and 6,7,10,11-THGG groups, respectively.…”

Pigment Analysis of “ Candidatus Chlorothrix halophila,” a Green Filamentous Anoxygenic Phototrophic Bacterium

“…The BChl a macrocycle is commonly esterified with phytol (BChl a P ). However, other alcohols, such as geranylgeraniol (GG), dihydrogeranylgeraniol (DHGG), and tetrahydrogeranylgeraniol (THGG), have also been observed in purple bacteria, usually at trace levels (20). In plants, these esterifying alcohols are thought to represent biosynthetic intermediates of Chl a GG to Chl a P (22,30).…”