Differences in kinetic properties of cytochrome oxidase in mitochondria from rat tissues. A comparative study.

Substrate kinetic properties of cytochrome oxidase in rat liver, kidney, brain and heart mitochondria were examined using ascorbate + N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) as the electron donor system. Analysis of the substrate kinetics data revealed tissue-specific expression of kinetic components exhibiting differences with respect to Km, Vmax and Kcat/Km values. Regression analysis data suggest that the enzyme activity may be regulated in a tissue-specific manner.