title: [Mg2,Ca2+-ATPase activity of sarcolemmas of intestinal smooth muscle cells in the rabbit].
abstract: Preparations of rabbit small intestine smooth muscle cell sarcolemma are capable of hydrolyzing ATP in the presence of millimolar concentrations of Mg2+ and Ca2+ and possess the activity of Mg2+,Ca2+-ATPase having a high affinity for Ca2+ (Km = 5.8 X 10(-6) M). The optimal conditions for the Mg2+,Ca2+-ATPase reaction were established. It was demonstrated that sarcolemmal preparations hydrolyze ATP, GTP, ITP and UTP almost at the same rates. The enzyme contains SH-groups that are unequally exposed to the water phase and are inhibited by 50% by p-chloromercurybenzoate and by 90% by dithionitrobenzoate. The Mg2+,Ca2+-ATPase activity is highly sensitive to oxytocin: at the concentration of 10(-7) MU/ml, the hormone completely inhibits the enzyme without affecting its Mg2+-, Ca2+- and Na+,K+-ATPase activities.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006868:Hydrolysis; D007421:Intestine, Small / Q000201:enzymology; D009130:Muscle, Smooth / Q000201:enzymology*; D011817:Rabbits; D012508:Sarcolemma / Q000201:enzymology*
chemical_list: D000255:Adenosine Triphosphate; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases
vernacular_title: Mg2+,Ca2+-ATPaznaia aktivnost' sarkolemmy gladkomyshechnykh kletok tonkoĭ kishki krolika.