1.2.1.79 succinate semialdehyde + NAD+ + H2O the enzyme activity in the presence of NADP+ is approximately 20fold higher than that measured in the presence of NAD+ 1.2.1.79 succinate semialdehyde + NADP+ + H2O the enzyme activity in the presence of NADP+ is approximately 20fold higher than that measured in the presence of NAD+ 1.2.1.79 succinate semialdehyde + NADP+ + H2O - 1.2.1.79 succinate semialdehyde + NADP+ + H2O data from crystal structures provide details about the catalytic mechanism by revealing a covalent adduct of a cofactor with the catalytic cysteine in the binary complex and a proposed thiohemiacetal intermediate in the ternary complex 1.2.1.79 succinic semialdehyde + NADP+ + H2O chemical mechanism based on functional data and structural information proposed, 1H-NMR to probe the stereospecificity of GabD1 show a transfer of the deuteride to the pro-R position of NADP+ indicating GabD1 has A-type stereospecificity