New insights into ergot alkaloid biosynthesis in Claviceps purpurea: An agroclavine synthase EasG catalyses, via a non-enzymatic adduct with reduced glutathione, the conversion of chanoclavine-I aldehyde to agroclavine

• Published in: Organic & biomolecular chemistry Vol. 9; no. 11; pp. 4328 - 4335
• Main Authors: Matuschek, Marco, Wallwey, Christiane, Xie, Xiulan, Li, Shu-Ming
• Format: Journal Article
• Language: English
• Published: England 07.06.2011
• Subjects: Aldehydes - chemistry; Aldehydes - metabolism; Aspergillus fumigatus; Biocatalysis; Claviceps - enzymology; Claviceps - metabolism; Claviceps purpurea; Clavicipitaceae; Ergolines - chemistry; Ergolines - metabolism; Ergot Alkaloids - biosynthesis; Ergot Alkaloids - chemistry; Ergot Alkaloids - genetics; Escherichia coli; Fungal Proteins - chemistry; Fungal Proteins - metabolism; Glutathione - chemistry; Glutathione - metabolism; Molecular Conformation; Molecular Sequence Data; Oxidoreductases Acting on CH-NH Group Donors - chemistry; Oxidoreductases Acting on CH-NH Group Donors - metabolism; Stereoisomerism; Trichocomaceae
• ISSN: 1477-0520; 1477-0539; 1477-0539
• DOI: 10.1039/c0ob01215g

Ergot alkaloids are indole derivatives with diverse structures and biological activities. They are produced by a wide range of fungi with Claviceps purpurea as the most important producer for medical use. Chanoclavine-I aldehyde is proposed as a branch point via festuclavine or pyroclavine to clavine-type alkaloids in Trichocomaceae and via agroclavine to ergoamides and ergopeptines in Clavicipitaceae. Here we report the conversion of chanoclavine-I aldehyde to agroclavine by EasG from Claviceps purpurea, a homologue of the festuclavine synthase FgaFS in Aspergillus fumigatus, in the presence of reduced glutathione and NADPH. EasG comprises 290 amino acids with a molecular mass of about 31.9 kDa. The soluble monomeric His(6)-EasG was purified after overproduction in E. coli by affinity chromatography and used for enzyme assays. The structure of agroclavine was unequivocally elucidated by NMR and MS analyses.