Kinetic analysis of a new human ornithine carbamoyltransferase variant.
A new human enzymatic variant was found in a patient with ornithine carbamoyltransferase (carbamoylphosphate:L-ornithine carbamoyltransferase, EC 2.1.3.3) deficiency. This mutant enzyme has decreased affinity, with an abnormal Km value for ornithine (3-5-times greater than control at all pH values). The maximal velocity (V) varied with pH as a normal enzyme but the sigmoid curve obtained (V vs. pH) is shifted towards alkaline pH values. The pK of the functional catalytic group is 8.3 instead of 6.65 of a control enzyme. At its optimum pH the V of the mutant enzyme is greater than the V of the normal enzyme. Other mutant enzyme proteins with abnormal affinity for ornithine have already been described. They all are different from the reported here.
D002675:Child, Preschool; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008297:Male; D009952:Ornithine / Q000378:metabolism; D009954:Ornithine Carbamoyltransferase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
D009952:Ornithine; D009954:Ornithine Carbamoyltransferase