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

摘要: Abstract Removal of zinc from thermolysin results in an inactive, metal-free apoenzyme. Zn2+, Co2+, and Mn2+, when added stoichiometric amounts, restore 100, 200, 10% the activity native enzyme. Fe2+ high molar excess restores about 60% activity. Zinc is bound much more firmly than cobalt, as shown by mutual displacement resultant enzymatic activities. that required to induce inhibits enzyme, seemingly binding a specific, inhibitory site. The atom does not seem contribute stability protein toward heat denaturation. Chelating agents, e.g. 1,10-phenanthroline, inhibit competing with enzyme for its removing it. inhibition fully reversible on dilution or addition Zn2+ ions function concentrations chelating agents. enzymatically active cobalt exhibits absorption circular dichroic spectra indicative unusual environment atom. There shoulder near 500 nm maximum at 555 (e ∼90). These data together spectral perturbations CD, magnetic dichroic, lead conclusion coordinated distorted tetrahedral geometry. This deduction consistent both those other cobalt-substituted enzymes which exhibit similarly properties compared Co(II) complex interpretations x-ray structure analysis thermolysin.