InterPro domain: IPR005097

This entry represents the NADP binding domain of saccharopine dehydrogenase. In some organisms this enzyme is found as a bifunctional polypeptide with lysine ketoglutarate reductase. The saccharopine dehydrogenase can also function as a saccharopine reductase [ 1 , 2 ].

Saccharopine dehydrogenase ( 1.5.1.10 ) catalyses the condensation of l-alpha-aminoadipate-delta-semialdehyde (AASA) with l-glutamate to give an imine, which is reduced by NADPH to give saccharopine [ 3 ]. In some organisms this enzyme is found as a bifunctional polypeptide with lysine ketoglutarate reductase (PF). Saccharopine dehydrogenase can also function as a saccharopine reductase. Saccharopine is an intermediate in lysine metabolism.

Homospermidine synthase (HSS) ( 2.5.1.44 ) catalyses the synthesis of the polyamine homospermidine from 2 putrescine molecules in an NAD ⁺ -dependent reaction [ 4 ]. HSS evolved from the alternative spermidine biosynthetic pathway enzyme carboxyspermidine dehydrogenase [ 5 , 6 ] and the structure of HSS is related to lysine metabolic enzymes [ 7 ].

1. Crystal structure of saccharopine reductase from Magnaporthe grisea, an enzyme of the alpha-aminoadipate pathway of lysine biosynthesis. Structure 8, 1037-47
2. Lysine metabolism in higher plants. Amino Acids 20, 261-79
3. Chemical mechanism of saccharopine reductase from Saccharomyces cerevisiae. Biochemistry 48, 5899-907
4. Purification, molecular cloning and expression in Escherichia coli of homospermidine synthase from Rhodopseudomonas viridis. Eur. J. Biochem. 240, 373-9
5. An alternative polyamine biosynthetic pathway is widespread in bacteria and essential for biofilm formation in Vibrio cholerae. J. Biol. Chem. 284, 9899-907
6. Evolution and multifarious horizontal transfer of an alternative biosynthetic pathway for the alternative polyamine sym-homospermidine. J. Biol. Chem. 285, 14711-23