Phenoloxidases in <i>Portabella</i> Mushrooms

Abstract

ABSTRACT Tyrosinase, laccase, and peroxidase activities were detected in crude extracts from commercial Portabella mushrooms. Tyrosinase was present in larger amounts than either laccase or peroxidase. Catechol showed the greatest activity as a substrate for tyrosinase while diaminobenzidine was found to be a good substrate for estimating laccase and peroxidase activity. Two tyrosinase and three laccase isoforms were detected after native electrophoresis. At least 10 tyrosinase isoforms were observed after isoelectric focusing. The distribution of these forms varied in different tissues. Browning reactions in Portabella mushrooms are a result of tyrosinase rather than laccase or peroxidase.