CARBON MONOXIDE-REACTIVE HAEMOPROTEINS OF YEAST

The yeasts Saccharomyces cerevisiae, Candida utilis and Saccharomyces carlsbergensis were shown to have two CO-binding haemoproteins in addition to cytochrome a3. These haemoproteins were separated by a method described. One, contained in the particulate fraction of the cells, was extracted by sodium deoxycholate and precipitated at 30% (NH4)2SO4 saturation. The visible spectrum was that of a B-type cytochrome, but it reacted with carbon monoxide to produce CO-difference transmission minima at 408 mμ, 540 mμ and 572 mμ. It did not form a complex with either CN- or O2. The other haemoprotein was separated from the non-particulate cellular fraction and precipitated at 65% (NH4)2SO4 saturation. Like the haemoglobin of blood, this haemoprotein can be oxygenated, reduced and oxidized and can react with CN- and CO. The CO-difference transmission minima are situated at 419 mμ, 532 mμ and 568 mμ. CO-difference reflectance spectrophotometry of C. utilis cells was employed for semi-quantitative estimation of the carbon monoxide complex of cytochrome a3 (CO-a3) and the CO complex of those haemoproteins with a 570 mμ CO-difference reflectance minimum (CO-Hp570). The concentration of CO-a3 and CO-Hp570 varied with glucose concentration and culture age. Evidence is presented for contribution to the CO-Hp570 of C. utilis by both cytochrome o and haemoglobin in high glucose cultures and by cytochrome o alone in low glucose cultures. © 1969.