Bacterial strain B-009, capable of using racemic 1,2-propanediol (PD), was identified as a rapid-growing member of the genus
Mycobacterium. The strain is phylogenetically related to
M. gilvum, but has slightly different physiological characteristics. An NAD
+-dependent enantioselective alcohol dehydrogenase, which acts on
R-PD, was purified from the strain. The enzyme was a homodimer of a peptide coded by a 1047-bp gene (
mbd1). A highly conserved sequence for medium-chain dehydrogenase/reductases with a preference for secondary alcohols was found in the gene. Hydroxyacetone was produced from
R-PD by an enzymatic reaction, indicating that position 2 of the substrate was oxidized. The enzyme activity was highest for (2
R,3
R)-2,3-butanediol (
R,
R-BD), enabling the enzyme to be identified as (2
R,3
R)-2,3-butanediol dehydrogenase (
R,
R-BD-DH). A homology search revealed
M. gilvum,
M. vanbaalenii, and
M. semegmatis to have ORFs similar to
mbd1, suggesting the widespread distribution of genes encoding
R,
R-BD-DH among mycobacterial strains.
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