Fig. 5.

Kinase activity of Frk. Partially purified Frk was assayed for kinase activity using either fructose (fru) or glucose (glu) as substrates. Activity was coupled to the production of NAD⁺ by PK and LDH and was measured at 340 nm for 2 min in a buffer containing 60 mM HEPES pH 7.5, 6 mM MgCl2, 3 mM ATP, 3 mM PEP, 0.3 mM NADH and 1/50 vol PK/LDH mix. Activity is plotted as μmol NAD⁺ produced per milligram protein over time. Data points represent the average ±sd of three biological replications.