METAL COORDINATION IN ZINC ENZYMES

We have studied the Bacillus Cereus exo-enzymes, phospholipase-C and s-lactamase II, by Zn and Co K-edge EXAFS. We report that the zincs in the structural and catalytic sites of the former enzyme are 5-coordinate, whereas cobalt, substituted in the catalytic site, is 6 coordinate. The s-lactamase II active site zinc has sulphur coordination, with either low occupancy or high Debye-Waller factor, in addition to imidazole coordination.