The enzymatic conversion of anthranilate to indolylglycerol phosphate in Neurospora crassa.

‘The formation of CDRPl from anthranilate and PP-ribose-P as well as the conversion of CDRP t,o InGP have been demonstrated in bacterial extracts (4). InGP synthetase, which catalyzes the conversion of CDRP to InGP, has been purified 17-fold from E. coli (5). While there has been no direct evidence that PR-anthranilate is an intermediate in this reaction sequence, recent studies with bacterial mutants suggest t,hat the over-all conversion is a 3-step reaction (3). In N. crassa, on the other hand, it would appear that only two gene products, or enzymes, are required to convert anthranilate to InGP. Extensive genetic studies have indicated that only two loci, the tryp-I locus and the tryp-4 locus, are involved in the control of this portion of the t.ryptophan pathway. The purification of the enzymes controlled by these two loci and the studies of the reactions which they catalyze are described in this paper. It is concluded that in N. crassa the synthesis of InGP from anthranilate is catalyzed by these two enzymes alone. Furthermore, the intermediate in the sequential reaction has been characterized as PR-anthranilate, not CDRP, the intermediate demonstrated in the bacterial system.