The tyrosinases of Fundulus heteroclitus at different stages of embryonic development.

The study described here was undertaken in an effort to determine whether multiple forms of tyrosinase (EC 1.10.3.1) are present in Fundulus heteroclitus during embryonic development. If they are present, do they appear simultaneously in the course of development and do they continue to be produced and maintained without change during the part of the life cycle when tyrosinase should normally be active? Multiple forms of tyrosinase have been found in Neurospora crassa (Sussman, 1961; Fox & Burnett, 1962; Fling, Horowitz & Heinemann, 1963), mushroom (Smith & Kruger, 1962; Bouchilloux, McMahill & Mason, 1963; Jolley & Mason, 1965), potato (Patil & Zucker, 1965), Drosophila melanogaster (Lewis & Lewis, 1963; Mitchell & Weber, 1965), the eggs of Rana pipiens (Turney, 1964), goldfish (Kim & Tchen, 1962; Kim, Tchen & Chavin, 1962), hamster melanoma (Pomerantz, 1963,1966) and mouse melanoma (Shimao, 1962; Burnett, Seiler & Brown, 1967). By using a variety of physical and chemical techniques to isolate the tyrosinases present in various organisms and organs, the investigators cited above have been able to establish numerous specific characteristics of the enzymes. Their published data suggest that in both plants and animals there may be variation in the chemical and physical characteristics of individual, enzymically active tyrosinase molecules. Experiments have not yet revealed, however, the metabolic or functional significance of the various forms of an enzyme within a single system. Since the presence of multiple forms of tyrosinase within a single system seems to be universal, it was anticipated from the outset that multiple forms of tyrosinase would be found in the embryos of Fundulus heteroclitus. The formation of melanin is catalysed in both plants and animals by the enzyme tyrosinase. In the presence of this enzyme, tyrosine is oxidized to 3,4-dihydroxyphenylalanine (DOPA) and DOPA, in turn, is oxidized to DOPAquinone. The conversion of DOPA-quinone to melanin proceeds in several steps (Lerner & Fitzpatrick, 1950). The presence of multiple forms of tyrosinase within a single organism or organ could be the result of chance mutations. Such mutations might cause subtle 1 Authors' address: The Department of Dermatology, Harvard Medical School, Massachusetts General Hospital, Boston, Massachusetts 02114, U.S.A.