title: Inhibition of lysozyme by polyvalent metal ions.
abstract: The rate of hen egg-white lysozyme (mucopeptide N-acetylmuramoylhydrolase, EC 3.2.1.17), catalysis was determined in the presence of various metal ions (Co2+, Zn2+ and eight of the trivalent lanthanide ions). In the assay system employed, the lanthanides were found to inhibit more strongly than either Zn2+ or Co2+. The inhibition data was fitted to several models of the interactions of the metal ion with the enzyme. These models ranged in complexity from a single inhibitory metal binding site on the enzyme (two-parameter fit) to the presence of two non-independent and non-equivalent inhibitory metal binding sites (five-parameter fit). The more complicated models did not fit the data more precisely than the simplest one-site model, suggesting that the adoption of the simpler model is warranted. The fact that the association constants obtained from the simplest analysis for Co2+ (1.3 +/- 1.9 . 10(2) M-1) and Gd3+ (7.0 +/- 2.6 . 10(3) M-1) are consistent with literature values determined from spectroscopic measurements further supports the validity of the simplest model.
mesh_terms: D003035:Cobalt / Q000494:pharmacology*; D004529:Egg White; D007700:Kinetics; D008674:Metals, Rare Earth / Q000494:pharmacology*; D009113:Muramidase / Q000037:antagonists & inhibitors*; D015032:Zinc / Q000494:pharmacology*
chemical_list: D008674:Metals, Rare Earth; D003035:Cobalt; D009113:Muramidase; D015032:Zinc