Metal Substitutions and Inhibition of Thermolysin: Spectra of the Cobalt Enzyme

Removal of zinc from thermolysin results in an inactive, metal-free apoenzyme.Znz+, Co2+, and Mn2+, when added in stoichiometric amounts, restore 100, ZOO, and 10% of the activity of the native enzyme.Fez+ in high molar excess restores about 60% of the native activity.Zinc is bound much more firmly than is cobalt, as shown by mutual displacement and the resultant enzymatic activities.Zinc in excess of that required to induce activity inhibits the enzyme, seemingly by binding to a specific, inhibitory site.The zinc atom