Arginase from Candida albicans

The enzyme arginase (EC 3.5.3.1.) catalyses the hydrolysis of L-arginine to equimolar amounts of L-ornithine and area. This enzyme was studied in Candida albicans, an opportunistic yeast which causes diseases ranging from superficial infections to the deep systemic disease, candidiasis, in immunosuppressed humans. The fungus was grown as yeast in synthetic medium containing L-arginine (pH 4.5) as the sole nitrogen source, at room temperature for various growth periods. The organism was also grown at pH 6.5 and at 37°C for pseudohyphal production. Arginase activity was measured from the cell-free homogenate. The maximal activity of arginase was at 12 h in the pseudohyphal phase and 72 h in the yeast phase. Among the different forms of nitrogen tested for arginase induction, arginine induced maximum arginase activity compared with others such as ammonia, glutamine and glutamate which induced comparatively less arginase activity. Saboraud dextrose broth, a complex medium, supported maximum growth of the organism, but tryptic soy broth supported maximum enzyme activity. The results also indicate that L-arginine is essential for arginase induction.