title: ATP hydrolysis kinetics of Na,K-ATPase in cataract.
abstract: The steady-state kinetics of hydrolysis of Mg2+ ATP by the epithelial Na,K-ATPase of individual human lenses were determined. Among the cataract lens population, four distinct kinetic types were observed: negative kinetic co-operativity. Michaelis-Menten kinetics, positive kinetic co-operativity, and substrate inhibition kinetics. Negative kinetic co-operativity and Michaelis-Menten kinetics were also observed in a group of presumably clear lenses from non-diabetic individuals ages 16-42 years. Substrate inhibition kinetics were found to be prevalent in individuals with mature onset diabetes. Substrate inhibition kinetics were also observed for Na,K-ATPase isolated from lenses which had been incubated in high glucose. It would appear that this modification leads to an inhibition of Na,K-ATPase-dependent K+ influx into these cultured lenses.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000293:Adolescent; D000328:Adult; D000818:Animals; D002386:Cataract / Q000209:etiology / Q000378:metabolism*; D002417:Cattle; D048909:Diabetes Complications; D003920:Diabetes Mellitus / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D007908:Lens, Crystalline / Q000378:metabolism*; D009924:Organ Culture Techniques; D011188:Potassium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: D000255:Adenosine Triphosphate; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium