Ergot alkaloid biosynthesis in Aspergillus fumigatus: conversion of chanoclavine-I to chanoclavine-I aldehyde catalyzed by a short-chain alcohol dehydrogenase FgaDH |
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Authors: | Christiane Wallwey Marco Matuschek Shu-Ming Li |
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Institution: | 1. Institut für Pharmazeutische Biologie, Philipps-Universit?t Marburg, Deutschhausstrasse 17A, 35037, Marburg, Germany
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Abstract: | Ergot alkaloids are toxins and important pharmaceuticals which are produced biotechnologically on an industrial scale. A putative gene fgaDH has been identified in the biosynthetic gene cluster of fumigaclavine C, an ergot alkaloid of the clavine-type. The deduced gene product FgaDH comprises 261 amino acids with a molecular mass of about 27.8 kDa and contains the conserved motifs of classical short-chain dehydrogenases/reductases (SDRs), but shares no worth mentioning sequence similarity with SDRs and other known proteins. The coding region of fgaDH consisting of two exons was amplified by PCR from a cDNA library of Aspergillus fumigatus, cloned into pQE60 and overexpressed in E. coli. The soluble tetrameric His6-FgaDH was purified to apparent homogeneity and characterized biochemically. It has been shown that FgaDH catalyzes the oxidation of chanoclavine-I in the presence of NAD+ resulting in the formation of chanoclavine-I aldehyde, which was unequivocally identified by NMR and MS analyzes. Therefore, FgaDH functions as a chanoclavine-I dehydrogenase and represents a new group of short-chain dehydrogenases. K M values for chanoclavine-I and NAD+ were determined at 0.27 and 1.1 mM, respectively. The turnover number was 0.38 s?1. |
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