Product-controlled steady-state kinetics between cytochrome aa3 from Rhodobacter sphaeroides and equine ferrocytochrome c analyzed by a novel spectrophotometric approach

► Steady state kinetics of R. sphaeroides cyt c oxidase and horse cyt c is monophasic. ► Full spectrum deconvolution used to obtain [cyt c2+] and [cyt c3+] at each point. ► Analysis shows product inhibition by cyt c3+ due to interaction at two sites. ► cyt c3+ is a competitive inhibitor at the catalytic site. ► cyt c3+ also binds at a second, allosteric site and modulates both KM and Vmax.