title: Tyrosinase activity in human ocular malignant melanoma.
abstract: We examined tyrosinase activity in pigmented specimens from three cases of ocular malignant melanoma. Tissue (cholate-trypsin-treated) extract was prepared in cholate-phosphate buffer by homogenization, centrifugation, trypsin digestion, and hydroxylapatite column chromatography. Tyrosinase activity was spectrophotometrically assayed as dopa (L-3,4-dihydroxylphenylalanine) oxidase activity. Tyrosinase activity was detected in the cholate-trypsin-treated extracts. Enzyme activity was inhibited by phenylthiourea but not by 3-iodo-tyrosine. The enzyme was inactivated when extract was preheated or digested with pronase. We believe that our findings confirm the presence of tyrosinase activity in ocular malignant melanoma.
mesh_terms: D000368:Aged; D004156:Catechol Oxidase / Q000378:metabolism*; D002830:Choroid Neoplasms / Q000201:enzymology*; D005260:Female; D006801:Humans; D008297:Male; D008545:Melanoma / Q000201:enzymology*; D008875:Middle Aged; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D009918:Orbital Neoplasms / Q000201:enzymology*; D013053:Spectrophotometry / Q000379:methods
chemical_list: D004156:Catechol Oxidase; D014442:Monophenol Monooxygenase