Stereochemistry during aflatoxin biosynthesis: cyclase reaction in the conversion of versiconal to versicolorin B and racemization of versiconal hemiacetal acetate

Article Abstract:

Stereochemical changes of substances formed during the conversion of versiconol hemiacetal acetate (VHA) to versicolorin A (VA) using chiral high-performance liquid chromatography showed that in cell-free experiments using the cystosol of Aspergillus parasiticus NIAH-26, both 2'S and 2'R versiconol acetate (VOAc) enantiomers were obtained from racemic VHA in the presence of NADPH and dichlorvos (dimethyl 2,2-dichlorovinylphosphate). The esterase activity catalyzing the conversion of VHA to versiconal (VHOH ) or of VOAc to versiconal did not indicate the stereospecificity for the 2' carbon atom of VHA or VOAc. When racemic VHA or VHOH was incubated with the cytosol, (I'R, 2'S)-(-)-VB was obtained.

Acetates

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Stereochemistry during aflatoxin biosynthesis: conversion of norsolorinic acid to averufin

Article Abstract:

The stereochemical relationship of norsolorinic acid (NA), averantin(AVN), hydroxyaverantin (HAVN) and averufin is assessed using high-performance liquid chromatography. Cell-free experiments using the crystal fractions of Aspergillus parasiticus NIAH-26, (1'S)-AVN was obtained from NA in the presence of NADPH. Only (1'S)-AVN served as a substrate for the reversible reaction of AVN leads to NA.

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The aspergillus parasiticus estA-encoded esterase converts versiconal hemiacetal acetate to versiconal and versiconol acetate to versiconol in aflatoxin biosynthesis

Article Abstract:

Aflatoxins are produced by fungi called aspergillus parasiticus, these toxins cause the rotting of agricultural produce. The main aim of this study is to determine the role of the estA gene in aflatoxin biosynthesis.

Science & research, Research, Aspergillus, Biosynthesis, Agricultural microbiology

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