Folcarelli S, Battistoni A, Falconi M, O'Neill P, Rotilio G, Desideri A
Department of Biology, University of Rome Tor Vergata, Italy.
Biochem Biophys Res Commun. 1998 Mar 27;244(3):908-11. doi: 10.1006/bbrc.1998.8364.
The catalytic activity of wild type Escherichia coli Cu,Zn superoxide dismutases and of two mutants in which two lysine residues conserved in most bacterial Cu,Zn superoxide dismutases have been replaced by serine was investigated by pulse radiolysis and Brownian dynamics simulations. Experimental and computational data show that neutralization of Lys60 strongly reduces the catalytic activity of the enzyme (approximately 50%), indicating that this residue has a primary role in the electrostatic attraction of the substrate towards the catalytic copper. Neutralization of Lys63 does not significantly influence the catalytic rate constant. The results suggest that prokaryotic Cu,Zn superoxide dismutases have evolved an electrostatic mechanism to facilitate the enzyme-substrate encounter that is functionally equivalent to that already found in the eukaryotic enzymes.
通过脉冲辐解和布朗动力学模拟研究了野生型大肠杆菌铜锌超氧化物歧化酶以及两个突变体的催化活性，在这两个突变体中，大多数细菌铜锌超氧化物歧化酶中保守的两个赖氨酸残基已被丝氨酸取代。实验和计算数据表明，Lys60的中和强烈降低了酶的催化活性（约50%），表明该残基在底物向催化铜的静电吸引中起主要作用。Lys63的中和对催化速率常数没有显著影响。结果表明，原核铜锌超氧化物歧化酶已经进化出一种静电机制，以促进酶与底物的相遇，这在功能上等同于真核酶中已发现的机制。
