Phenol oxidase activity and pigment synthesis in conidiospores ofPenicillium cyclopium

Abstract

Phenol oxidase (PO) of Penicillium cyclopium belongs to the laccases (E.C. 1.14.18.1). By PAA-gel electrophoresis three forms of the enzyme were detected. Most of the PO in emerged sporulating cultures accumulates in the cell wall of the conidiospores. However, a high percentage is not bound to the wall constituents and can be easily removed with aqueous solutions. This soluble fraction was 570-fold enriched by (NH4)2SO4-precipitation, followed by chromatography on sephadex G 200 and on hydroxylapatite-cellulose, The necessity of PO for conidiospore pigmentation was shown by means of suspended spores whose rates of pigment accumulation resemble those of conidia maturing in situ. Pigmentation is stopped if PO is inhibited by diethyldithiocarbamate. This corresponds to the fact that in strains with heavily pigmented conidiospores PO activity is much higher than in strains with weakly pigmented or unpigmented spores. Also the time course of PO accumulation in the latter strains is different from that of the former. Furthermore, in mutant res-eth 1 which has unpigmented conidiospores, PO isoenzyme no. 3 could not be detected.