Substitution of arginine for lysine 134 alters electrostatic parameters of the active site in shark Cu,Zn superoxide dismutase

The complete amino acid sequence was determined for the Cu,Zn superoxide dismutase from the shark Prionace glauca. The active site region shows the substitution of an Arg for Lys at position 134, which is important for electrostatic facilitation of the diffusion of O2- to the catalytically active copper. This change may be related to observed alterations of electrostatic parameters of the enzyme (pK of the pH dependence of the enzyme activity, rate of inactivation by H2O2), although it preserves a high efficiency of dismutation at neutral pH.