On the chemical mechanism of succinic semialdehyde dehydrogenase (GabD1) from Mycobacterium tuberculosis

► GabD1 is a NADP+-specific succinic semialdehyde dehydrogenase. ► Hysteresis is an artifact in the absence of a divalent metal activator, such as Mg2+. ► Hydride transfer is only partially rate-limiting. ► Enzyme or substrate isomerization is rate limiting for the overall reaction. ► Stereochemistry is S for the thiohemiacetal and R for hydride transfer.