Steady-state kinetics of electron transfer through cytochrome chain of uncoupled submitochondrial particles. II. Influence of pH on kinetics of electron transfer.

pH Dependences of steady-state kinetic parameters of cytochrome chains of submitochondrial particles have been studies. It has been shown that the lifetimes of activated states (tau) of the pairs of cytochromes b leads to c1 and a leads to a3 have different pH dependences; those for the c1 leads to c and c leads to a cytochrome pairs being similar. The rate constants for the non-activated state of the respiratory chains decreased for the b leads to c1 pair and increased for the a leads to a3 pair when the pH value was increased. The values of pK calculated from these dependences for the pairs b leads to c1 and a leads to a3 were 7.2 and 8.9, respectively. It has been supposed that the ratio of activated to non-activated electron carriers may be controlled by the local pH value in the mitochondrial membrane, the latter being dependent upon the rate of electron transfer. The kinetic model based on this assumption allows one to explain the experimental dependences on pH of the rate constants for cytochromes b leads to c, and a leads to a3. The values of the diffusion rate constants for H+ and OH- ions in the mitochondrial membrane estimated from these kinetic data obtained in this study were 10(4)--10(5) s-1 and 10(2)--10(3) s-1, respectively.