If the hydroxyl group indicated by the arrow is phosphorylated, the coenzyme is called NADP + . Because the redox chemistry occurs specifically at the nicotinamide part of the molecule, typically the ...If the hydroxyl group indicated by the arrow is phosphorylated, the coenzyme is called NADP + . Because the redox chemistry occurs specifically at the nicotinamide part of the molecule, typically the rest of the molecule is simply designated as an 'R' group. At the beginning of the reaction cycle, both the ketone substrate and the NADH cofactor are bound in the enzyme's active site, and C 4 of the nicotinamide ring of NADH is positioned very close to the carbonyl carbon of the ketone.
