title: 13C NMR evidence for bacteriochlorophyll c formation by the C5 pathway in green sulfur bacterium, Prosthecochloris.
abstract: The 13C NMR spectra of the pheophorbide of bacteriochlorophyll c, formed in the presence of L-[1-13C]glutamate and [2-13C]glycine and [13C]bicarbonate in Prosthecochloris aestaurii, were analysed. The isotope in the glutamate was specifically incorporated into the eight carbon atoms in the tetrapyrrole macrocycle derived from the C-5 of 5-aminolevulinic acid, while no specific enrichment of these eight carbon atoms was observed in the spectrum of the pigment formed in the presence of [2-13C]glycine. These labelling patterns provide evidence for the operation of the C5 pathway of 5-aminolevulinic acid synthesis for bacteriochlorophyll c formation in the bacterium. The labelling of bacteriochlorophyll c by [13C]bicarbonate is consistent with its formation from 5-[1,4,5-13C]aminolevulinic acid formed by the C5 pathway from [1,2,5-13C]glutamic acid. It is proposed that this glutamate is the transamination product of 2-[1,2,5-13C]oxoglutaric acid, arising by carboxylation of [1,4-13C]succinyl-CoA with 13CO2 catalysed by 2-oxoglutaric acid synthase activity, and that the labelled succinyl-CoA is, in turn, derived by the fixation of 13CO2 by the reductive tricarboxylic acid cycle. The 13C chemical shifts of two sp2 quaternary carbons of bacteriopheophorbide c methyl ester (C-2 and C-4) were reassigned.
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D001426:Bacterial Proteins / Q000096:biosynthesis*; D001429:Bacteriochlorophylls; D002244:Carbon / Q000378:metabolism; D002247:Carbon Isotopes; D002250:Carbon Radioisotopes; D005971:Glutamates / Q000378:metabolism; D005998:Glycine / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy
chemical_list: D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; D002247:Carbon Isotopes; D002250:Carbon Radioisotopes; D005971:Glutamates; C002084:bacteriochlorophyll c; D002244:Carbon; D005998:Glycine