Presence of tyrosinase activity in human ciliary body.

We examined tyrosinase activity in pigmented tissues from five human eyes. Tissue 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 extracts of the ciliary body. Enzyme activity was inhibited by phenylthiourea but not by 3-iodo-tyrosine. We believe that our findings confirm the presence of tyrosinase activity in the human ciliary body.