Purification and properties of anthranilate synthetase from the ergot fungus, Claviceps spec., strain SD 58

Abstract

A three-enzyme complex containing anthranilate synthetase, phosphoribosyl anthranilate isomerase and indole-3-glycerol phosphate synthetase was partially purified from Claviceps spec., strain SD 58. The anthranilate synthetase activity of the enzyme complex was quite unstable unless glutamine, MgCl2, TRIS and, most importantly, glycerol were included in the extraction buffer. The three-enzyme complex showed a molecular weight of 400,000 when estimated using Sephadex gel filtration, and a molecular weight of 200,000 when using sucrose density gradient centrifugation. At least two bands of anthranilate synthetase were detected on disc gel electrophoresis. An enzyme complex containing phosphoribosyl anthranilate synthetase and indoleglycerol phosphate synthetase, but no anthranilate synthetase, was isolated from Claviceps. This enzyme complex had an apparent molecular weight of 165,000 as estimated by sucrose gradient centrifugation. Anthranilate synthetase is inhibited by L-tryptophan and elymoclavine, the terminal ergot alkaloid produced by this strain of Claviceps. No differences could be detected between the enzyme complexes isolated from 2-day-old growing mycelia and from 6-day-old alkaloid-producing mycelia of the organism.