tailieunhanh - Báo cáo khoa học: Metabolic pathways leading from amino acids to vitamin B12 in Propionibacterium shermanii, and the sources of the seven methyl carbons

The metabolic pathways leading froml-[2-13 C]aspartic acid, [2-13 C]glycine andl-[methyl-13 C]methionine to vitamin B12were investigated, focusing on the biosynthetic pathways leading to the aminopropanol moiety of vita-min B12and on the role of the Shemin pathway leading tod-aminolevulinic acid (a biosynthetic intermediate of tetrapyrrole), by means of feeding experiments with Propionibacterium shermaniiin combination with 13 C-NMR spectroscopy. | ễFEBS Journal Metabolic pathways leading from amino acids to vitamin B12 in Propionibacterium shermanii and the sources of the seven methyl carbons Katsumi lida and Masahiro Kajiwara Department of MedicinalChemistry Meiji PharmaceuticalUniversity Tokyo Japan Keywords 13C-NMR 2-13C glycine L- 2-13C aspartic acid L- methyl-13C methionine vitamin B12 biosynthesis Correspondence K. Iida and M. Kajiwara Department of Medicinal Chemistry Meiji Pharmaceutical University 2-522-1 Noshio Kiyose-shi Tokyo 204-8588 Japan Fax 81 424 95 8612 Tel 81 424 95 8611 E-mail iida@ kajiwara@ Received 29 June 2007 revised 3 August 2007 accepted 3 August 2007 doi The metabolic pathways leading from L- 2-13C aspartic acid 2-13C glycine and L- methyl-13C methionine to vitamin B12 were investigated focusing on the biosynthetic pathways leading to the aminopropanol moiety of vitamin B12 and on the role of the Shemin pathway leading to ỗ-aminolevulinic acid a biosynthetic intermediate of tetrapyrrole by means of feeding experiments with Propionibacterium shermanii in combination with 13C-NMR spectroscopy. The 13C-methylene carbons of L- 2-13C aspartic acid which is transformed to 2-13C glycine via L- 2-13C threonine and 2-13C glycine added to the culture medium served mainly to enrich the seven methyl carbons of the corrin ring through C-methylation by S-ade-nosyl-L- methyl-13C methionine derived from catabolically generated L- methyl-13C methionine in the presence of tetrahydrofolic acid. The results indicate that the catabolism of these amino acids predominates over pathways leading to 2R -1-amino-2-propanol or ỗ-aminolevulinic acid in P. shermanii. Feeding of L- methyl-13C methionine efficiently enriched all seven methyl carbons. In the cases of 2-13C glycine and L- methyl-13C methionine the 13C-enrichment ratio of the methyl carbon at C-25 the site of the first C-methylation was less than those of the other six methyl carbons .