The Oxygen Affinity of a Flavin Oxidase Involved in the Respiration of Streptococcus faecalis.

Abstract
The oxygen affinity of the terminal respiratory enzyme of Streptococcus faecalis, an organism which is devoid of cytochromes and whose respiration is insensitive to cyanide, was determined. The respiratory rate of intact cells and the activity of the extracted DPNH oxidase are essentially independent of the oxygen tension when the reaction systems "were gassed with 5, 20 and 100% 03. The oxygen affinity (I/Km) of 4 x 105[image]is unusually high for a flavin oxidase, and the implications of this finding for the analysis of respiratory mechanisms are discussed.