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.