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

Abstract
The 600 MHz 1H 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 Nϵ 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.