1.5.1.10 N6-(L-1,3-dicarboxypropyl)-L-lysine + NADP+ + H2O = L-glutamate + (S)-2-amino-6-oxohexanoate + NADPH + H+ - - 1.5.1.10 N6-(L-1,3-dicarboxypropyl)-L-lysine + NADP+ + H2O = L-glutamate + (S)-2-amino-6-oxohexanoate + NADPH + H+ ordered kinetic mechanism, the reduced dinucleotide substrate binds to enzyme first followed by L-alpha-aminoadipate-delta-semialdehyde, which adds in rapid equilibrium prior to L-glutamate, saccharopine is released prior to NADP+, primary deuterium kinetic isotope effects and solvent deuterium kinetic isotope effects, overview. A conformational change to open the site and release products (in the direction of saccharopine formation) is the rate limiting step. Two groups are involved in the acid-base chemistry of the reaction. An enzyme group with a pKa of 5.6 accepts a proton from the alpha-amine of glutamate to generate the neutral amine that can act as a nucleophile. The alpha-amine of glutamate attacks the carbonyl of the semialdehyde to generate the carbinolamine, which is protonated by a second enzyme group with a pKa of about 7.8-8.0. Ionizable residues that might play a role in the acid-base mechanism of the enzyme are D126, C154 and/or Y99 741780