EFFECT OF PH ON BRDICKA CURRENTS PRODUCED BY CYTOCHROME-C

Effect of pH and buffer concentrations on Brdièka currents produced by horse heart cytochrome c was investigated in the presence of hexaamminecobalt(HI) chloride in ammonia, tris(hydroxymethyl)aminomethane, N,N-dimethylglycine, borate, and carbonate buffer solutions at pH varying between 8.2 and 10.7. The Brdiéka current-Activity of the protein varied with pH and the kind and concentration of buffers, but, if corrected for the effect of the buffer salts, showed a sigmoidal pH-dependence. The pH-dependence was interpreted as due to the protonic dissociation of Lys-79 of the protein. Brdiéka currents of the protein were observed also in unbuffered solutions containing no proton donor except water. The current intensity was explained by taking into account the change of pH at electrode surface. The results indicate that a main proton donor in die Brdièka reaction is a water molecule. © 1980 The Chemical Society of Japan.