Identification and characterization of two families of F420 H2-dependent reductases from Mycobacteria that catalyse aflatoxin degradation.

Aflatoxins are polyaromatic mycotoxins that contaminate a range of food crops as a result of fungal growth and contribute to serious health problems in the developing world because of their toxicity and mutagenicity. Although relatively resistant to biotic degradation, aflatoxins can be metabolized by certain species of Actinomycetales. However, the enzymatic basis for their breakdown has not been reported until now.

Cloning, expression, purification, crystallization and preliminary X-ray studies of a pyridoxine 5'-phosphate oxidase from Mycobacterium smegmatis.

Pyridoxine 5'-phosphate oxidases (PNPOxs) are known to catalyse the terminal step in pyridoxal 5'-phosphate biosynthesis in a flavin mononucleotide-dependent manner in humans and Escherichia coli. Recent reports of a putative PNPOx from Mycobacterium tuberculosis, Rv1155, suggest that the cofactor or catalytic mechanism may differ in Mycobacterium species. To investigate this, a putative PNPOx from M.

Metabolon formation in dhurrin biosynthesis.

Synthesis of the tyrosine derived cyanogenic glucoside dhurrin in Sorghum bicolor is catalyzed by two multifunctional, membrane bound cytochromes P450, CYP79A1 and CYP71E1, and a soluble UDPG-glucosyltransferase, UGT85B1 (Tattersall, D.B., Bak, S.

The in vitro substrate regiospecificity of recombinant UGT85B1, the cyanohydrin glucosyltransferase from Sorghum bicolor.

The in vitro substrate specificity of UDP-glucose:p-hydroxymandelonitrile-O-glucosyltransferase from Sorghum bicolor (UGT85B1) was examined using a range of potential acceptor molecules, including cyanohydrins, terpenoids, phenolics, hexanol derivatives and plant hormones. Qualitative enzyme activity assays employing 20 different putative substrates were performed and 15 proved to be glucosylated using recombinant UGT85B1 isolated from Escherichia coli. K(m) and k(cat) values were determined for nine of these substrates including mandelonitrile, geraniol, nerol and beta-citronellol, 2-hydroxy-3-methoxybenzyl alcohol, 1-hexanol, cis-3-hexen-1-ol, 3-methyl-3-buten-1-ol and 3-methyl-2-buten-1-ol.