Reconstitution of the apoenzyme of cytochrome oxidase from Pseudomonas aeruginosa with heme d1 and other heme groups.

Cytochrome oxidase (EC 1.9.3.2) from Pseudomonas aeruginosa contains heme d1 and heme c in an equimolar ratio. The heme d1 can be removed from the enzyme with acidified acetone leaving an apoenzyme that contains heme c but has no oxidase activity. Reconstitution of the apoenzyme in neutral 6 M urea with heme d1 yields a reconstituted product which, after removal of the urea, has 90 to 100% of the oxidase activity of the native enzyme, a 1:1 molar ratio of the heme groups, and is indistinguishable from the native on the basis of its absorption spectral properties and its EPR spectrum. The apoenzyme can also be reconstituted with heme a, deuteroheme, hematoheme, mesoheme, and protoheme but only the heme a yields a product with any oxidase activity. The properties of these reconstituted products are compared.