Single mutation at the intersubunit interface confers extra efficiency to Cu,Zn superoxide dismutase

The Val28-->Gly single mutant at the subunit interface of Cu,Zn superoxide dismutase from Photobacterium leiognathi displays a k(cat)/K(M) value of 1.7x10(10) M(-1) s(-1), twice that of the native enzyme. Analysis of the three-dimensional structure indicates that the active site Cu,Zn center is not perturbed, slight structural deviations being only localized in proximity of the mutation site. The enzyme-substrate association rate, calculated by Brownian dynamics simulation, is identical for both enzymes, indicating that the higher catalytic efficiency of the Val28-->Gly mutant is not due to a more favorable electrostatic potential distribution. This result demonstrates the occurrence of an intramolecular communication between the mutation site and the catalytic center, about 18 A away and indicates a new strategy to encode extra efficiency within other members of this enzymatic family.