The occurrence,and the significance,of tyrosinase in the reproductive organs of certain amphibians

Abstract

Tyrosinase—the enzyme which oxidizes tyrosin to produce a black, insoluble, pigment-like compound—has been shown by Phisalix (C. R. Soc. Biol., 50, p. 793, 1898) to occur in the skin of the European frog, Rana esculenta. Gessard, later (ibid., 56, p. 285, 1904), shows that the same enzyme occurs in the skin of the toad, Bufo vulgaris, and in the frog, Rana temporaria. In discussing the importance of the tyrosinase Phisalix says: “It is probable that the oxidase presides over the oxidations within the organism … and plays the role of fixing oxygen in cutaneous respiration.” If such is the case, and the production of the pigment in the skin is only a secondary reaction, or the elimination of a byproduct, the study of this enzyme becomes of much greater importance than merely as a pigment-producer.

In every instance where the mechanism of melanin formation has been elucidated, it has been found that pigmentation is due to the interaction of tyrosinase and a chromogen. It therefore seemed probable that the enzyme might be present in the ovaries of those amphibians which deposit pigmented eggs, and might be responsible for the pigment formation.

In every instance where the mechanism of melanin formation has been elucidated, it has been found that pigmentation is due to the interaction of tyrosinase and a chromogen. It therefore seemed probable that the enzyme might be present in the ovaries of those amphibians which deposit pigmented eggs, and might be responsible for the pigment formation. I have found that tyrosinase is present in the ovaries of the green frog, Rana clamata, and the wood frog, Rana sylaatica. Owing to the greater ease in securing material of various ages most of the tests were carried out using material from the green frog.