Agaricus bisporus tyrosinase—II. Characterization of hydroxylase and dehydrogenase activities

Abstract

1. 1. Preparative Isoelectric focusing (PIEF) was used to isolate hydroxylasic and dehydrogenasic activities, at different pI. 2. 2. The fraction at pI 4.7 and 4.9 displays a pure dehydrogenase activity (substrate l-DOPA). 3. 3. This fraction did not react with tyrosine, either in the spot-test or in absorption spectra (200–620 nm), and did not exhibit any oxygen consumption. 4. 4. The fraction at pI 4.1 and 4.3 reacted with both l-DOPA and tyrosine as substrate, showing dehydrogenase and hydroxylase activity. 5. 5. The latter activity was confirmed by the oxygen consumption test, showing that molecular oxygen is used to ortho-hydroxylate tyrosine.