| Description | Aspartate-semialdehyde dehydrogenase ( ), the second enzyme in the aspartate pathway, converts aspartyl phosphate to aspartate-semialdehyde, the branch point intermediate between the lysine and threonine/methionine pathways. Based on sequence alignments, the aspartate-semialdehyde dehydrogenase family appears to have at least three distinct subfamilies. Most studies have been performed on enzymes isolated from Gram-negative bacteria [ , , , ]. The N-terminal domain forms the active site and NADP-binding pocket, while C-terminal domain is primarily involved in hydrophobic intersubunit contacts. The catalytic mechanism involves the formation of a covalent thioester acyl-enzyme intermediate mediated through nucleophilic attack by an active site cysteine residue on the substrate aspartyl phosphate. Release of inorganic phosphate is followed by hydride transfer from NADPH to yield the product. The recently described archaeal structure suggests that the two subgroups of aspartate semi-aldehyde dehydrogenase share similar structures and have an identical catalytic mechanism, despite their relatively low sequence identity []. Unlike the bacterial enzymes, the archaeal enzyme utilised both NAD and NADP as cofactor.This entry represents the subgroup of aspartate dehydrogenases found primarily in organisms lacking peptidoglycan. In addition to its role in aspartate metabolism, the enzyme from Sulfolobus solfataricus has been shown recently to exhibit RNase activity, suggesting that these enzymes may perform additional cellular functions [].This entry also matches malonyl-CoA reductases from archaeal Metallosphaera and Sulfolobus spp, which have sequence identity to aspartate-semialdehyde dehydrogenase, suggesting a common ancestor for both proteins [ ]. | Name | Aspartate-semialdehyde dehydrogenase, peptidoglycan lacking |
| Short Name | Asp_semi-ald_DH_pep-lack | Type | Family |
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