Arginine metabolism in Saccharomyces cerevisiae. Some general properties of yeast arginase

Cells of Saccharomyces cerevisiae ATCC 9763 were cultured aerobicallyat 30?C in defined media containing arginine as a sole sourceof nitrogen. After 5 hr of growth arginase (L-arginine ureohydrolaseEC 3.5.3.1[EC]) was extracted by sonication and partially purifiedby gel filtration. The specific enzyme activity was increasedthirty times as a result of Sephadex G-200 treatment. The geltreated enzyme was stable for at least 3 days when stored at2?C. Enzyme activity was maximal at pH 9.2 and was increasedby preincubation with divalent metallic ions. The apparent Michaelisconstant for arginine was 12.5 mM in glycinate buffer and 250mil in phosphate buffer. The enzyme was strongly inhibited byL-ornithine. The kinetics of this inhibition revealed that ornithinecompeted with arginine for the active site. The molecular weightof yeast arginase was estimated to be 120000?10000 by determinationof elution volumes from Sephadex G-200. The general propertiesof the yeast enzyme are discussed in relation to (a) arginasesfrom other sources and (b) regulation of the Krebs-Henseleitcycle in Saccharomyces. (Received January 27, 1973; )