Localization of L-asparaginase in Pseudomonas aeruginosa

Whole cells of Pseudomonas aeruginosa possess L-asparaginase activity. The enzyme is released by suspension in 0.2 M MgCl2 and resuspension in 0.1 M Tris buffer, pH 8.4. Under these conditions neither the plasma membrane enzyme, NADH oxidase, nor the scluble enzyme, lactic acid dehydrogenase, are released. The L-asparaginase and the periplasmic alkaline phosphatase are completely inactivated by treatment of whole cells with diazonaphthalene–disulfonic acid, a reagent which does not penetrate the cytoplasmic membrane. Under the conditions used no inactivation of NADH oxidase or lactic acid dehydrogenase was observed. L-Asparaginase is also released by converting whole cells to spheroplasts. The results suggest that L-asparaginase of P. aeruginosa is located exterior to the cytoplasmic membrane, possibly in the periplasmic space.