Na+, K+-dependent adenosine triphosphate phosphohydrolase. Two types of kinetics

Kinetic analysis of hydrolytic activity of (Na+, K+)-ATPase purified from duck salt glands shows that several substrates are hydrolysed in different manners. UTP, GTP and ITP are hydrolysed in accordance with usual Michaelis kinetics with the single Km value and with no cooperatively (Hill coefficient, nH = 1), while CTP is hydrolysed, like ATP, in accordance with non-Michaelis kinetics with two Km values. Hydrolysis of the last two substrates in the range of the second Km is characterised by positive cooperativity with nH greater than 1.