NAD+ and NADH regulate an ATP-dependent kinase that

NAD+ and NADH regulate an ATP-dependent kinase that

ABSTRACT Crude extracts of Escherichia coil contain a
protein kinase, El-K, that phosphorylates enzyme I (El) of the
phosphoenolpyruvate:glycose phosphotransferase system
(PTS). Phosphorylation occurs at the active site hsdine
residue. The activity of EI-K was lost during purifiation.
However, kinase activity was restored by adding NAD+ or
NADP+. NADH reversed NAD+ activation of the knse, and
the level of EI-K activity was dependent on the NAD+/NADH
ratio. Although crude preparations of EI-K showed no NAD+
requirement, they were completely inhibited by NADH, either
in the assay mi or when the enzyme was pretreated and the
NADH was removed prior to the assay. NAD+ rse full
activity to the NADH-pretreated inactive fractions. The results
suggest that EI-K contain a bound cofactor that Is lost during
purification and that may be analogous to NAD+. EI-K activity
may serve to link some of the diverse functions of the PTS, such
as sugar transport, to the metabolic state of the cell.

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