Purification and properties of tyrosinases from Vibrio tyrosinaticus

Abstract

Two tyrosinase isoenzymes (EC1. 10.3.1) have been highly purified from Vibrio tyrosinaticus . This represents the first characterization of tyrosinases from eubacteria. The enzymes have molecular weights of 41,000 and 38,500, closer to the tyrosinase of Neurospora crassa (33,000) than to the mammalian enzymes from mouse and hamster melanoma (55,000 and 70,000). The bacterial tyrosinases are also different from the mammalian enzymes in that the former possess basic isoelectric points. The Vibrio tyrosinases do not cross-react with antiserum against a hamster melanoma tyrosinase. The K m values for l -tyrosine are 3.1 m m for both isoenzymes while the K m value for l -DOPA is 36 m m for one and 67 m m for the other. The values for tyrosine are tenfold, and those for dopa about 100-fold, larger than the corresponding K m values for the tumor enzymes. Apoenzyme was prepared by treatment with diethyldithiocarbamate, and activity was partially or wholly restored by addition of Cu 2+ , Mn 3+ , Cd 2+ , or Fe 2+ . The one isoenzyme examined has some activity on d -tyrosine and very slight activity against d, l - m -tyrosine. No activity was detected with catechol or l -phenylalanine.