The Conversion of Cytochrome Oxidase to an Inactive Form of the Enzyme by Water Dialysis

Abstract

A modification of beef-heart cytochrome oxidase that results in loss of catalytic capacity has been produced by extensive dialysis of the enzyme against water. The enzyme after dialysis retains all the heme, 80% of the phospholipid, and 60% of the copper originally associated with it. A comparison of the circular-dichroism (C.D.) spectra of the two forms has led to the conclusion that the heme of the enzyme is randomly oriented in the dialyzed form. Analysis of the rate at which this randomization occurs has shown that it is not the primary event occurring during dialysis. Prior to the loss of the C.D. spectrum of the dialyzed material there is a loss of enzymatic activity. Attempts to regenerate the original from the water-dialyzed enzyme by incubating the latter with a phospholipids–cholate mixture have been unsuccessful.