1H NMR spectroscopy of the binuclear Cu(II) active site of Streptomyces antibioticus tyrosinase

The 600 MHz H-1 NMR spectrum of tyrosinase (31 kDa) of Streptomyces antibioticus in the oxidized, chloride-bound form is reported, The downfield part of the spectrum (15-55 ppm) exhibits a large number of paramagnetically shifted signals. The paramagnetism is ascribed to a thermally populated triplet state. The signals derive from six histidines binding to the metals through their NE atoms. There is no evidence for endogenous bridges. The exchange coupling, -2J, amounts to 298 cm(-1). In the absence of chloride the peaks broaden. This is ascribed to a slowing down of the electronic relaxation. The exchange coupling decreases to -2J = 103 cm(-1) (C) 1999 Federation of European Biochemical Societies.