The formation of arginine dihydrolase by streptococci and some properties of the enzyme system.

The lack of any breakdown of urea under the experimental conditions led to the conclusion that urease was not present in streptococci and that urea could not be an intermediate in the reaction. Thus it seems likely that the formation of ornithine from arginine by these bacteria occurred by a pathway different from that possessed by arginase of mammalian liver. Niven et al. (1942) tested the ability of streptococci to liberate ammonia from a yeast extract-tryptone-glucose-arginine medium. Every strain which produced ammonia gave a stronger test for ammonia in the medium which contained arginiIne than in the control. Gale (1945) found that the ability of various group D streptococci to utilize arginine was directly related to their arginine dihydrolase activity. It also was reported that cells formed very early in the growth cycle (3 hours) were more active on arginine than cells harvested at a later time. Roche et al. (1948, 1950) indicated that arginine dihydrolase also exists in Pseudomonas ovalis. Examination of the enzyme in this organism is complicated by the presence of a creatinase, creatininase, and glycocyaminase. Pseudomonas species also contain urease (Hino, 1924). Our knowledge of the arginine dihydrolase enzyme system is very meager.