title: Substrate stereoselectivity of mammalian D-aspartyl endopeptidase.
abstract: The formation and accumulation of D-aspartate residue (D-Asp) in proteins caused by oxidative stress leads to dysfunction and/or denaturation of proteins, and is consequently responsible for aging-related misfolding diseases such as cataracts, prion disease, and Alzheimer's disease. We sought to identify that an unknown protease selectively degrades the noxious D-Asp-containing protein, namely D-aspartyl endopeptidase (DAEP), and finally purified it from the inner mitochondrial membrane of mouse liver. In order to analyze the substrate stereoselectivity of DAEP, we synthesized a peptide corresponding to 55-65 (Thr-Val-Leu-Asp-Ser-Gly-Ile-Ser-Glu-Val-Arg) of human αA-crystallin and its corresponding diastereoisomers in which L-α-Asp was replaced with L-β-, D-α- or D-β-Asp residue at position 58. Following incubation of that peptide with purified DAEP, it was only degraded at D-α-Asp(58), independent of ATP or NAD. This result indicates that DAEP stereoselectively recognizes and degrades its substrate at the internal D-α-Asp residue. DAEP therefore seems to physiologically serve as the quality control system against the noxious D-Asp-containing protein in the long life span of mammals.
authors.affiliation: Div. of Radiation Life Science, Dept. of Radiation Life Science and Radiation Medical Science, Research Reactor Institute, Kyoto University, Sennan-gun, Osaka 590-0494, Japan. kinouchi@rri.kyoto-u.ac.jp
authors.forename: Tadatoshi
authors.initials: T
authors.lastname: Kinouchi
authors.forename: Norihiko
authors.initials: N
authors.lastname: Fujii
authors.forename: Noriko
authors.initials: N
authors.lastname: Fujii
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D000375:Aging; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003459:Crystallins / Q000737:chemistry / Q000378:metabolism; D026603:D-Aspartic Acid / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008099:Liver / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D051336:Mitochondrial Membranes; D009243:NAD / Q000737:chemistry / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: C511246:CRYAA protein, human; D003459:Crystallins; D010455:Peptides; D009243:NAD; D026603:D-Aspartic Acid; D000255:Adenosine Triphosphate; D016282:Aspartic Acid Endopeptidases