Adenosine triphosphatase activity of Ureaplasma urealyticum

Adenosine triphosphatase activity of U. urealyticum is an integral membrane-bound protein which cannot be detached from the membrane by mild treatment with EDTA in low-ionic strength media nor by ionic detergents which rapidly inactivated the enzyme. The enzyme was Mg++ dependent; Mn++ and Co++ could replace Mg++ to some extent. A slight stimulatory effect was also exerted by sodium and lithium. The enzyme showed a nucleotide triphosphatase activity, but ADP was hydrolyzed at close to 40% the rate of ATP and other nucleotide monophosphatase were hydrolyzed at a very slow rate. Oubain and oligomycin did not inhibit the adenosine triphosphatase activity, whereas DCCD, NBD-Cl and several sulfhydryl-blocking reagents strongly reduced its activity. The enzyme could not be stimulated by trypsin pretreatment. It seems that the complex enzyme is tightly linked to the lipid bilayer of the membrane and differs in many aspects from the F0-F1 (Mg++, Ca++)-ATPase of bacteria.