Adenosine Triphosphatase Activity of Mycoplasma Membranes

Abstract

Adenosine triphosphatase activity of Mycoplasma laidlawii, M. gallisepticum and Mycoplasma sp. strain-14 was confined to the cell membrane. The enzymatic activity was dependent on magnesium, but was not activated by sodium and potassium. Ouabain did not inhibit the adenosine triphosphatase activity of the mycoplasmas, and did not interfere with the active accumulation of potassium by M. laidlawii cells. Sulfhydryl-blocking reagents and fluoride inhibited the enzymatic activity, whereas 2,4-dinitrophenol was without any effect. Membranes of M. laidlawii hydrolyzed other nucleotidetriphosphatesand adenosine diphos-phate (ADP), but at a lower rate than adenosine triphosphate (ATP). Nucleoside-2[image]-(3[image])-phosphates, ribose-5-phosphate, glucose-6-phos-phate, and pyrophosphate were not hydrolyzed by the membrane preparations. It seems that the enzyme(s) involved in ATP hydrolysis by M. laidlawii membranes is strongly bound to the membrane subunits, which would account for the failure to purify the enzyme by protein fractiona-tion techniques. The adenosine triphosphatase activity of mycoplasma membranes resembles in its properties that of similar enzymes studied in bacteria. The mycoplasma enzyme (s) seems to differ from the adenosine triphosphatase associated with ion transport in mammalian cell membranes and from mitochondrial adenosine triphosphatase.