Origin of the carbon atoms of biotin 13 C‐NMR studies on biotin biosynthesis in Escherichia coli

• Published in: European journal of biochemistry Vol. 220; no. 2; pp. 585 - 591
• Main Authors: IFUKU, Ohji, MIYAOKA, Hiroaki, KOGA, Nobuyoshi, KISHIMOTO, Jiro, HAZE, Shin‐ichirou, WACHI, Youji, KAJIWARA, Masahiro
• Format: Journal Article
• Language: English
• Published: 01.03.1994
• ISSN: 0014-2956; 1432-1033
• DOI: 10.1111/j.1432-1033.1994.tb18659.x

The origin of the carbon atoms of pimeloyl‐CoA, the earliest known precursor in the pathway of de novo biotin biosynthesis in Escherichia coli , was investigated by 13 C‐NMR spectroscopy. In fermentation of the biotin‐overproducing DRK332/pXBA312 strain of Escherichia coli (a repressor mutant carrying a biotin operon fragment in the plasmid), a high dose of L‐alanine (8 g/l) stimulated dethiobiotin and biotin accumulation. Although L‐alanine is a known precursor of 7‐keto‐8‐aminopelargonic acid in biotin biosynthesis, the 13 C‐NMR spectrum of dethiobiotin showed that the C‐3 of L‐[3‐ 13 C]alanine was incorporated into not only the methyl carbon (C‐9) but also alternate carbons (C‐2, C‐4, C‐6) of the side chain, and these latter positions are the same as those labeled with D‐[1‐ 13 C]glucose. These data indicate that L‐alanine can act as an alternative carbon source, suggesting that acetyl‐CoA is a possible precursor for pimeloyl‐CoA synthesis. In accordance with this hypothesis, the C‐1 of sodium (1‐ 13 C)acetate and the C‐2 of sodium (2‐ 13 C)acetate were incorporated into alternate carbons in the side chain of dethiobiotin, i.e., (C‐1, C‐3, C‐5, C‐7) and (C‐1, C‐2, C‐4, C‐6), respectively. These results suggested firstly that in E. coli pimeloyl‐CoA is biosynthesized from L‐alanine and/or acetate via acetyl‐CoA, but not via pimelic acid, which has been suggested as a biotin precursor in other species, and secondly that the carboxyl group of biotin originates from carbon dioxide produced through the tricarboxylic acid cycle.