Abstract
The first part of the paper is devoted to separation and characterization of tyrosinase of Notophthalmus viridescens. After ammonium sulfate fractionation and DEAE-cellulose chromatography, a fraction of extract was obtained which had a 1000-fold increase in enzyme activity and revealed one positive DOPA oxidase band and one negative protein band on acrylamide gel electrophoresis. Some characterization of the enzyme was made using this sample. Specific activity of this fraction was estimated to be 39 × 10 −2 μmole of l-tyrosine/mg in 17 hr. An inhibitor of tyrosinase was demonstrated in the Notophthalmus lens. In the second part of the paper, the level of tyrosinase activity was followed in the iris tissue as it was transformed into the lens after lentectomy in adult N. viridescens. When the activity was based on micrograms of DNA, the dorsal iris increased slightly in activity during the phase of depigmentation. A significant increase in activity was recorded when the lens had been formed by completely depigmented dorsal iris cells. On the other hand, in the ventral iris, where weak depigmentation is followed by repigmentation, the activity level showed a weak increase. Implication of the data for tissue transformation was discussed.
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