Purification and Gene Cloning of a Dehydrogenase fromLactobacillus brevisThat Catalyzes a Reaction Involved in Aflatoxin Biosynthesis

Abstract

When 10 strains of lactic acid bacteria were incubated with 5'-hydroxyaverantin (HAVN), a precursor of aflatoxins, seven of them converted HAVN to averufin; the same reaction is found in aflatoxin biosynthesis of aflatoxigenic fungi. These bacteria had a dehydrogenase that catalyzed the reaction from HAVN to 5'-oxoaverantin (OAVN), which was so unstable that it was easily converted to averufin. The enzyme was purified from Lactobacillus brevis IFO 12005. The molecular mass of the enzyme was 100 kDa on gel filtration chromatography and 33 kDa on SDS polyacrylamide gel electrophoresis (SDS-PAGE). The gene encoding the enzyme was cloned and sequenced. The deduced protein consisted of 249 amino acids, and its estimated molecular mass was 25,873, in agreement with that by time of flight mass spectrometry (TOF MS) analysis. Although the deduced amino acid sequence showed about 50% identity to those reported for alcohol dehydrogenases from L. brevis or L. kefir, the commercially available alcohol dehydrogenase from L. kefir did not convert HAVN to OAVN. Aspergillus parasiticus HAVN dehydrogenase showed about 25% identity in amino acid sequence with the dehydrogenase and also with these two alcohol dehydrogenases.

Genetics of Dothistromin Biosynthesis of Dothistroma septosporum: An Update

“…Some Lactobacillus brevis strains have a homolog of the AF adhA dehydrogenase, which was able to convert AF precursor 5-hydroxyaverantin to averufin in feeding studies. The same reaction is found in aflatoxin biosynthesis, although L. brevis does not produce AF or any precursors [ 47 ].…”

Role of DptE and DptF in the lipidation reaction of daptomycin

“…Another possibility for lipidation of secondary metabolites could be the interaction of fatty acid synthase‐like enzymes or substrates from the primary metabolism with NRPSs or PKSs, as shown for aflatoxin produced by the fungi Asparagillus parasiticus and A. flavus [39,40]. In this example, the fatty acid synthase‐like enzymes HexA and HexB synthesize hexanoic acid from acetyl CoA and two units of malonyl CoA.…”