The role of riboflavin in the formation and disposal of hydrogen peroxide by streptococcus faecalis.

Certain strains of Streptococcus faecalis when grown under highly aerobic conditions acquire a mechanism that permits them to oxidize a number of substrates without accumulating H202, and in addition enables them to rid the medium of added H202 during the metabolism of these substrates (Seeley and VanDemark, 1951). This mechanism does not involve catalase or the common hematin-containing peroxidase found in vegetable material. In considering the chemistry of this reaction, attention is drawn to two outstanding possibilities: (1) a spontaneous reaction between H202 and a compound such as pyruvate, and (2) a reaction, possibly enzyme mediated, between H202 and a reduced hydrogen carrier. The assumption of a reaction between pyruvate and H202 would not satisfy the fact that less oxygen is required by organisms grown under oxidative conditions to dissimilate a unit of glucose aerobically than is required by the same strain grown under anaerobic conditions (Seeley and VanDemark, 1951). The possibility of peroxide reacting with a reduced hydrogen carrier would explain nicely the known facts inasmuch as a given amount of oxygen could function twice as a hydrogen acceptor, the second time in the form of hydrogen peroxide. The well-defined participation of riboflavincontaining compounds in the direct union of hydrogen and oxygen in certain enzyme systems led us to consider a reduced form of riboflavin rather than a carrier such as coenzyme I as a possible reactor with peroxide. The present paper deals with additional aspects of the peroxidation reaction, and in particular, with the influence of riboflavin.