THE FORMATION OF ARGININE DIHYDROLASE BY STREPTOCOCCI AND SOME PROPERTIES OF THE ENZYME SYSTEM,

Abstract

Cellular suspensions of 2 strains of group D streptococci decompose arginine in accordance with the equation:[long dash][image] The reaction proceeds to approx. 90% of completion. Ornithine was detd. by a decarboxylase prepn. from Escherichia coli. Streptococci grown in the absence of added arginine possessed a low dihydrolase activity (QCO26), whereas cells grown in the presence of arginine possessed a high dihydrolase activity (QCO2 140). Arginine did not serve as a readily available C source for growth although the cells possessed strong dihydrolase. activity. The addition of glucose in 0.3 to 1% concn. resulted in a large increase in yield of cells with no change in QCO2. The fermentation of glucose and arginine during the growth cycle was followed by serial analysis. The cells formed in the first 5 hrs. of incubation did not contain significant dihydrolase activity. 70% of the total yield of cells was formed before fermentation of arginine occurred. Most of the dihydrolase was synthesized during the period of arginine fermentation. The culture pH during this period was near the pH for opt. dihydrolase activity in cellular suspensions. A culture medium for the opt. production of cells possessing an active arginine dihydrolase system is described. Arginine dihydrolase is stable in cold storage in both fresh and lyophilized cellular prepns. The opt. pH for both prepns. ranged from 5.8 to 6.3 with a peak at 6. The enzyme activity was not inhibited by a 6-fold increase in substrate above saturation level, and the dissociation constant of the enzyme-substrate complex was calculated to be 4.1 x 10-3[image]. The enzyme was specific for arginine. In cell-free extracts the conversion of arginine to citrulline required no co-factors, whereas the conversion of citrulline to ornithine required muscle adenylic acid, inorganic phosphate and divalent ions.