A gene, cobA + hemD, from Selenomonas ruminantium encodes a bifunctional enzyme involved in the synthesis of vitamin B12

McKay DB., B. Entsch, PJ. Anderson

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)

Abstract

Coenzymes derived from vitamin B12 (cyanocobalamin) are particularly important for core metabolism in ruminant animals. Selenomonas ruminantium, a Gram-positive obligate anaerobe isolated from cattle, is the main contributor of vitamin B12 to such ruminant animals. In nature, there are both aerobic and anaerobic pathways for B12 synthesis - the latter is only partly elucidated. Until now, there has been no investigation of B12 synthesis in S. ruminantium, which must use an anaerobic pathway. This paper reports the cloning of the chromosomal operon from S. ruminantium which is responsible for the first committed steps in corrinoid synthesis. Five open reading frames were found in the cloned fragment. All deduced amino acid sequences had similarity to defined proteins in the databases that are involved in porphyrin and corrin synthesis. Of particular interest is the gene designated cobA + hemD, which encodes a single polypeptide possessing two catalytic functions - uroporphyrinogen III synthase and uroporphyrinogen III 2,7-methyltransferase. This enzyme converts hydroxymethylbilane to precorrin-2. The functions of the protein coded by cobA + hemD were established by heterologous expression in Escherichia coli. The CobA activity has been demonstrated for three distinct types of proteins - monofunctional, bifunctional with siroheme formation and, this report, bifunctional with uroporphyrinogen III synthesis. The type found in S. ruminantium (cobA + hemD) is probably restricted to obligately anaerobic fermentative bacteria.
Original languageEnglish
Pages (from-to)63-70
Number of pages8
JournalGene
Volume281
Publication statusPublished - 2001

Fingerprint

Dive into the research topics of 'A gene, cobA + hemD, from Selenomonas ruminantium encodes a bifunctional enzyme involved in the synthesis of vitamin B12'. Together they form a unique fingerprint.

Cite this