Specific activity of L-glutaminase (E.C 3.5.1.2) was determined by isolating and partially purifying it from Penicillium chrysogenum using ammonium sulfate (85%). Upon addition of maleic anhydride (MA) and succinic anhydride (SA) to the reaction media at different concentrations (0.2, 0.4, 0.6, 0.8, and 1.0 mM), the enzyme was shown to be inhibited. The activity of the enzyme was reduced at a concentration of 10 mM by the four chelating agents ethylene glycol tetraacetate (EGTA), ethylenediaminetetraacetate (EDTA), phenannthroline, and dipyridyl, suggesting that the enzyme is a metalloenzyme. Metal cations such as CoCl2, CuCl2, FeCl3, and MgCl2 in the reaction media at a concentration of 10 mM shown to be inhibitory to the enzyme. Nevertheless, calcium chloride enhanced the enzyme activity at an equivalent concentration.