The catecholase activity of Neurospora tyrosinase.

A highly purified preparation of tyrosinase from Neurospora crassa was isolated with a view to elucidating its mechanism of action. Both the resting and functioning molecular weights of the enzyme were determined as 33000 plus or minus 2000 and kinetic data in conjunction with binding studies indicated the presence of only one site within the enzyme for binding phenolic substrates. Kinetic constants for several 0-diphenols and for the inhibitors cyanide and benzoic acid were determined and the kinetics are consistent with a mechanism in which either the substrates are bound in a random order or the diphenol binds first. The enzyme forms an oxygenated complex and a complex with hydrogen peroxide and both are detectable spectroscopically