Harding-passey mouse-melanoma tyrosinase inactivation by reaction products and activation by L-epinephrine.

1. Harding-Passey mouse-melanoma tyrosinase (EC 1.14.18.1) is inhibited during L-3,4-dihydroxyphenylalanine oxidation by reaction products. L-3,4-dihydroxyphenyl 3-[14C]alanine oxidation products bind to the enzyme, as demonstrated by gel electrophoresis and radioactivity measurements. 2. The enzyme interacts with indoles and oxidizes dopamine and norepinephrine. 3. L-epinephrine activates tyrosinase at non hormonal concentrations and bovine serum albumin protects the enzyme from auto-inhibition. 4. The inhibition of the Harding-Passey mouse-melanoma tyrosinase, during substrate oxidation, is very similar to that of mushroom enzyme.