The covalently bound flavin prosthetic group of β-cyclopiazonate oxidocyclase

Abstract

It has been reported that /3-cyclopiazonate oxidocyclase from Penicillium cyclopium, an enzyme which catalyzes the dehydrogenation and cyclization of P-cyclopiazonic to a-cyclopiazonic acid, contains covalently bound flavin [I] . A flavin peptide, rele: sed by digestion with pronase has been partially purified and preliminary results suggested that the flavin is at the dinucleotide level. The present paper is the first report of a collaborative study between the laboratories in South Africa and in San Francisco, aimed at defining the structure of the flavin site of this enzyme. It has been found that the flavin is attached to the protein by way of the 8 (Y group, as in other enzymes containing covalently bound flavin [2] and that the amino acid substituent is histidine, as in succinate dehydrogenase [3,4] but the nature of the linkage of the flavin to the imidazole is different from that in succinate dehydrogenase. The unusual properties of the flavin peptide from