Fig. 4. Transient-state GDH kinetics. (a) Typical absorbance profiles at 340 nm over 100 s showing four distinguishable phases of GDH-catalyzed glutamate oxidation in aCSF containing 0.1 mg mL⁻¹ GDH, 250 μM NAD⁺ and 5 mM glutamate in the absence (black) and presence (red) of 16 μM Yb³⁺ by stopped-flow spectroscopy. (b) Rate constants of the rate-determining NADH release in phase IV obtained by fitting the absorbance profile during 10–1500 s using two consecutive one-order kinetic modeling. Error bars represent standard error of the mean (n = 3, t-test, ***P < 0.001).