Figure 6. Ca²⁺ does not inhibit cytochrome c ²⁺ oxidase activity of D477A mutant COX from P.denitrificans.

D477A mutant COX (1.5 nM) in the basic medium with 0.4 M choline chloride. Oxidation of 10 µM reduced cytochrome c is followed spectrophotometrically in a dual-wavelength mode at 550 nm vs the 535 nm reference. Trace 1 (dotted line), control recording with no calcium added; trace 2, 200 µM CaCl₂ added where indicated. Trace 3, the same conditions as in trace 2 but with 2.5 nM bovine heart COX.