Cytochrome oxidase and its derivatives. II. The action of strong alkali on cytochrome oxidase

Abstract

By the action of strong alkali (0·1 to 0·3n ) cytochrome oxidase is converted to a Schiff’s base (aldimine) with practically the same absorption spectrum as that of the Schiff’s bases formed at high pH from other haemoproteins a (Lemberg & Newton 1962). Cytochrome oxidase, however, differs from the other haemoproteins a in that a higher pH (more than 12·5, rather than more than 9·5) is required for the reaction. At a pH above 13·5, but not at pH 12·5 to 13·0, the reaction of the ferric oxidase is preceded by the liberation of free haematin a . The products from both cytochromes a and a 3 at a pH above 12·5 react with carbon monoxide and with cyanide and have become indistinguishable. The complete disappearance of the 554 nm absorption band of ferrous cytochrome oxidase by the Schiff’s base formation indicates that this band, like that at 517 nm , is a genuine β. band of the oxidase and is not due to admixed cytochrome c 1 . Adding HCl to an alkaline pyridine solution of the Schiff’s base sufficient to neutralize the alkali gives the spectrum of pyridine haemochrome a directly. The haem in obtained by treatment of the Schiff’s base with acetone-HCl, followed by removal of the protein by extraction of the haematininto ether, gives haem in a ; after addition of pyridine, alkali and dithionite, only the 587 nm absorption band of pyridine haemochrome a is seen without any bands in the 575 to 582 nm region.