Cytochrome oxidase and its derivatives - III. Spectrophotometric observations on the modification of cytochrome oxidase by alkali and urea

Abstract

When cytochrome oxidase was exposed to a pH of 9 to 11.5, or to 8M urea, it was gradually altered into a haemoprotein (or possibly into a mixture of two very similar haemoproteins) which closely resemble the haemoproteins α formed by combination of haem α with proteins such as globins or serum albumins (Lemberg et al 1962) in their absorption spectra as well as in those of the carbon monoxide and cyanide com pounds. The same reaction is rapid at pH13 and precedes the aldimine formation described in the preceding paper. In this alteration the α-band of the ferrous oxidase is shifted from 605 to 595 nm, the γ-band from 445 to 436 nm. The α-band maximum of the CO-oxidase spectrum is shifted from 605 to 600 nm, with a disappearance of the shoulder at 590 nm due to CO-cytochrome a₃; the γ-band maximum is shifted from 430 to 434 nm with a disappearance of the shoulder at 444 nm due to cytochrome a not reacting with carbon monoxide. These findings confirm previous evidence that both cytochromes α and α₃ are haemoproteins derived from haem α. They also throw some light on the nature of the difference between them.