A tyrosinase, enzyme A, and a laccase, enzyme B, have been partially purified from larval cuticle of the flesh fly Sarcophaga bullata. Enzyme A (EC 1.10.3.1, o-diphenol: O2 oxidoreductase) oxidizes o-diphenols but not p-diphenols, is strongly inhibited by phenylthiourea, and has a pH optimum around pH 6.5–7.0. Assays on intact cuticle suggest that it becomes maximally activated at pH between 8 and 9. Enzyme B (EC 1.10.3.2, p-diphenol: O2 oxidoreductase) oxidizes both o-diphenols and p-diphenols, is not inhibited by phenylthiourea but is inhibited by concentrations of sodium azide that have little effect on enzyme A, and has a pH optimum near pH 4.5. Enzyme A was identified in extracts of cuticle from nine other species representing five orders. Enzyme B was much less readily extractable but was partially purified from larval cuticle of Phormia regina, Musca domestica, and Lucilia sericata. A summary of all species studied to date makes possible the test of a hypothesis about the distribution of these cuticular phenoloxidases within the Insecta.
Comparison of sucrose intake and production of elimination spots among adult Musca domestica, Musca autumnalis, Phormia regina and Protophormia terraenovae
