FIG. 3.

Thermal stability of GST-tagged wild-type and mutant glucokinase (A and B). Response of GST-glucokinase mutants to inhibition with glucokinase regulatory protein (GKRP) (C and D). GST-glucokinase levels were 22 nmol/l in all tests. A: Effect of glucose concentration on expressed GST-tagged glucokinase with ins454A and M197I hyperinsulinism mutations and the known E300K instability mutant. For M197I, the studies were not extended below the glucose S_0.5 of 2.6 mmol/l. B: Effect of temperature on mutant glucokinase enzyme activities. For these assays, enzymes were incubated for 30 min with glucose levels at their respective S_0.5. C and D: Inhibition of glucokinase activity by glucokinase regulatory protein measured in the presence and absence of sorbitol-6-phosphate (S6P), respectively. ○, ins454A; □, M197I; ◇, E300K; X, wild type.