The Oxidation State of Copper in Resting Tyrosinase

Abstract

Abstract Resting tryosinase was diamagnetic between 1.4 K and 200 K. Redox titration showed that it, but not apotyrosinase, contained a titrable group, E'0 = +0.36 volt (pH 7.0), n = 2. Upon denaturation with acid under strictly anaerobic conditions, the EPR-detectable copper increased from less than 5% of the copper present to about 100%. It is concluded that the active site of the enzyme contains a pair of antiferromagnetically coupled Cu2+ ions.