Uiterkamp A J, Mason H S
Proc Natl Acad Sci U S A. 1973 Apr;70(4):993-6. doi: 10.1073/pnas.70.4.993.
The T(r) and T[unk] states of tyrosinase were treated with NO. EPR spectra of the products observed at 14 degrees K and at 113 degrees K showed mixtures of two signals. One had components in the region of g = 2, about 1200 G wide, and in the region of g = 4, showing hyperfine splitting. The other signal was similar to that arising from isolated Cu(II) ions in an axially symmetric environment. The first signal was indicative of Deltam = 1 and Deltam = 2 transitions arising from magnetic dipole-dipole coupled Cu(II) ion pairs. It closely resembled previously reported EPR spectra obtained from NO-treated hemocyanin, which were confirmed in this study. The normal Curie behavior of the signals between 230 degrees K and 14 degrees K ruled out significant exchange coupling between the ion pairs. The Deltam = 2 signals were not saturable up to 350 mW at 14 degrees K. The broad Deltam = 1 signals could be separated from accompanying signals by the saturation characteristics of the latter at about 10 mW at 14 degrees K. The results establish the presence of a pair of copper ions at the active site of tyrosinase, and a clsoe structural relationship between this active site and that of hemocyanin.
用一氧化氮处理酪氨酸酶的T(r)和T[unk]状态。在14K和113K下观察到的产物的电子顺磁共振光谱显示出两种信号的混合物。一种信号在g = 2的区域有成分，宽度约为1200G，在g = 4的区域显示出超精细分裂。另一种信号与轴对称环境中孤立的Cu(II)离子产生的信号相似。第一个信号表明磁偶极 - 偶极耦合的Cu(II)离子对产生了Δm = 1和Δm = 2跃迁。它与先前报道的用一氧化氮处理血蓝蛋白得到的电子顺磁共振光谱非常相似，本研究对此进行了证实。在230K至14K之间信号的正常居里行为排除了离子对之间显著的交换耦合。在14K下，高达350mW时，Δm = 2信号不饱和。在14K下，约10mW时，通过后者的饱和特性，宽的Δm = 1信号可以与伴随信号分离。结果证实了酪氨酸酶活性位点存在一对铜离子，并且该活性位点与血蓝蛋白的活性位点之间存在密切的结构关系。
