Studies on the Biosynthesis of Corrinoids and Porphyrinoids. X.Biosynthetic Studies of Bacteriochlorophyll-a in Rhodopseudomonas spheroides: Incorporation of 2H, 13C and 15N-Labeled Substrates and Origin of the Hydrogen Atoms.

Abstract

The biosynthetic pathway of bacteriochlorophyll-a in Rhodopseudomonas spheroides was investigated by administration of [2-13C]glycine, L-[methyl-13C]methionine, L-[1-13C]glutamic acid and 13C- or 15N-labeled δ-aminolevulinic acid (ALA). The origin of the hydrogen atoms was studied by following the incorporation into bacteriochlorophyll of 13C-labeled ALA in a medium containing 50% D2O and that of 2H-, 13C-labeled ALA. The labeled bacteriochlorophylls were converted into more stable methyl bacteriopheophorbides, which were subjected to 13C-NMR analyses to obtain information about the biosynthetic origin of the hydrogen atoms. The use of 13C-enriched bacteriochlorophylls and methyl bacteriopheophorbides allowed us to make 13C-NMR signal assignments for all carbons of the porphyrin nucleus.