A mitochondrial chemiluminescence evoked by a novel mixed copper(II)-cyanide complex/acetaldehyde cyanohydrin chelate: A kinetic analysis suggesting a role for membrane-bound vicinal sulfhydryls

Abstract

Cyanide added to mitochondria in the presence of copper and acetaldehyde evokes a chemiluminescence which follows series pseudo-first-order kinetics: A ▪ B ▪ C + light . An evaluation of the effects of protein (mitochondria), copper, cyanide, acetaldehyde, and oxygen on the kinetic parameters shows that k 1 is influenced by protein, cyanide (at low concentrations), and oxygen while k 2 is influenced by cyanide, acetaldehyde (at low, <11.9 m m, and high, >35.6 m m, concentrations), and oxygen. The integral light increases linearly with the square root of total copper(II) and with the square of the total acetaldehyde. The sustained emissions appear to reflect an initial oxidative event mediated by a novel mixed copper(II)-cyanide complex/acetaldehyde cyanohydrin chelate. Cu(I) formed by the reduction of Cu(II), probably by mitochondrial vicinal sulfhydryls, reacts with dioxygen to form an O 2-copper complex which reacts with acetaldehyde to form the acetyl-1-hydroxyhydroperoxyl radical. This radical disproportionates by the Russell mechanism to generate electronically excited singlet and triplet carbonyl functions and singlet oxygen species whose emissive relaxations to the ground state display as the observed chemiluminescence. The kinetic evidence indicates that there are two Cu(I)-oxygen cyanide complexes transferring O ▪ to acetaldehyde. This evidence addresses the mechanisms of autoxidation of low-molecular-weight Cu(I) complexes with dioxygen. A suggested role for the involvement of vicinal sulfhydryl groups in the reactions is shown, kinetically, by the influence of copper and acetaldehyde on the integral light.