A Primitive Pathway of Porphyrin Biosynthesis and Enzymology in Desulfovibrio vulgaris

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 95; no. 9; pp. 4853 - 4858
• Main Authors: Ishida, Tetsuo, Yu, Ling, Akutsu, Hideo, Ozawa, Kiyoshi, Kawanishi, Shosuke, Seto, Akira, Inubushi, Toshiro, Sano, Seiyo
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 28.04.1998; National Acad Sciences; National Academy of Sciences; The National Academy of Sciences
• Subjects: Absorption spectra; Acetates; Bacteria; Biochemistry; Biological Sciences; Biosynthesis; Chromatography, Thin Layer; Coproporphyrinogens; Coproporphyrinogens - metabolism; Coproporphyrins; Culture Media; Desulfovibrio vulgaris - metabolism; Enzymes; Esters; Lactones - chemistry; Mass Spectrometry; Molecular Weight; Porphyrins; Porphyrins - biosynthesis; Porphyrins - chemistry; Protoporphyrins; Spectrophotometry; Uroporphyrinogens; Uroporphyrinogens - metabolism; Uroporphyrins
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.95.9.4853

Culture of Desulfovibrio vulgaris in a medium supplemented with 5-aminolevulinic acid and L-methionine-methyl-d3resulted in the formation of porphyrins (sirohydrochlorin, coproporphyrin III, and protoporphyrin IX) in which the methyl groups at the C-2 and C-7 positions were deuterated. A previously unknown hexacarboxylic acid was also isolated, and its structure was determined to be 12,18-didecarboxysirohydrochlorin by mass spectrometry and1H NMR. These results indicate a primitive pathway of heme biosynthesis in D. vulgaris consisting of the following enzymatic steps: (i) methylation of the C-2 and C-7 positions of uroporphyrinogen III to form precorrin-2 (dihydrosirohydrochlorin); (ii) decarboxylation of acetate groups at the C-12 and C-18 positions of precorrin-2 to form 12,18-didecarboxyprecorrin-2; (iii) elimination of acetate groups of the C-2 and C-7 positions of 12,18-didecarboxyprecorrin-2 to form coproporphyrinogen III; and (iv) conversion of coproporphyrinogen III; to protoporphyrin IX via protoporphyrinogen IX. We isolated the following three enzymatic activities involved in steps i-iii from the soluble fraction of the cells by anion-exchange chromatography: S-adenosyl-L-methionine:uroporphyrinogen III methyltransferase, precorrin-2 12,18-acetate decarboxylase, and 12,18-didecarboxyprecorrin-2 2,7-decarboxymethylase; all enzymic products were converted into autooxidized methyl esters and analyzed by thin-layer chromatography, UV-visible (UV-VIS) absorption, and mass spectrometry. The enzymatic reactions in D. vulgaris shed new light on porphyrin biosynthesis at an early stage in the evolution of prokaryotes.