Enzyme, Protein, Carbohydrate, and Phenolic Contaminants in Commercial Tyrosinase Preparations: Potential Problems Affecting Tyrosinase Activity and Inhibition Studies

Commercial mushroom tyrosinase contains other proteins, enzymes, carbohydrates, and phenolic material besides tyrosinase. Carbohydrate and phenolic material comprise a large percentage of the powder resuspensions derived from Agaricus bisporus. Enzyme assays identified the presence of tyrosinase, laccase, beta-glucosidase, beta-galactosidase, beta-xylosidase, cellulase, chitinase, xylanase, and mannanase in the commercial tyrosinase. Protein sequencing indicated the presence of tyrosinase, a lectin, and a putative mannanase as well as 10 unidentified protein/peptides in the commercial tyrosinase preparations. Characteristics of tyrosinase isoforms were similar in two different commercial tyrosinase sources. Inhibition studies indicated that l(50) values for some tyrosinase inhibitors were different when the crude powder was compared to a partially purified tyrosinase. The presence of these contaminants has the potential to affect studies using commercial tyrosinase.