Direct regulation of cytochrome c oxidase by calcium ions.

ABSTRACT: Cytochrome c oxidase from bovine heart binds Ca(2+) reversibly at a specific Cation Binding Site located near the outer face of the mitochondrial membrane. Ca(2+) shifts the absorption spectrum of heme a, which allowed previously to determine the kinetics and equilibrium characteristics of the binding. However, no effect of Ca(2+) on the functional characteristics of cytochrome oxidase was revealed earlier. Here we report that Ca(2+) inhibits cytochrome oxidase activity of isolated bovine heart enzyme by 50-60% with Ki of ∼1 µM, close to Kd of calcium binding with the oxidase determined spectrophotometrically. The inhibition is observed only at low, but physiologically relevant, turnover rates of the enzyme (∼10 s(-1) or less). No inhibitory effect of Ca(2+) is observed under conventional

SUBMITTER: Vygodina T 

PROVIDER: S-EPMC3769247 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature