Regulation of the cytosolic and melanosome-bound tyrosinase activities in harding-passey mouse melanoma

Abstract

1. 1. Mouse melanoma tyrosinases exist in the cytoplasm of melanocytes and also in a particulate form, bound to melanosomes. 2. 2. The cytosolic isoenzyme activity is not expressed in the melanocytes in vivo. One of the mechanisms for the activity regulation is the existence of a soluble inhibitor. This inhibition is non-competitive with regard to l-dopa. 3. 3. Particulate tyrosinase can be solubilized from the melanosome by several agents, Brij 35 and Triton X-100 being the most effective ones. Melanin accumulation in the organelle produces a competitive inhibition of the activity.