Characterization of a phenol oxidase from Cryptococcus neoformans var. neoformans

In Cryptococcus neoformans, enzymic oxidation of various catechols leads to melanin, a proposed virulence factor. A phenol oxidase enzyme of Cryptococcus neoformans var. neoformans produced at 25 C has been purified from an ultracentrifugal supernatant of an extract of broken cells. Hydrophobic interaction chromatography followed by anion-exchange column chromatography allowed purification of the phenol oxidase. The molecular weight of the enzyme estimated by gel filtration was about 80,000 and a dimeric species (Mw = 160,000) was suggested. The isoelectric point of the protein was approximately 4.1. An NH2-terminal 31 amino acid sequence was determined using phenol oxidase electroblotted onto a PVDF membrane after nondenaturing gel electrophoresis. Upon searching the Peptide Institute (Osaka) data base, no proteins with high degrees of homology were found.