title: Gliap--a novel untypical L-asparaginase localized to rat brain astrocytes.
abstract: L-asparaginases catalyse the formation of the neuroactive amino acid L-aspartate by deamination of asparagine. The major pathophysiological significance of L-asparaginase activity is in its clinical use for the treatment of acute lymphatic leukaemia and neoplasias that require asparagine and obtain it from circulating pools. Here we report the identification and characterization of Gliap, a cytosolic L-asparaginase, which is the founding member of a new group of L-asparaginases in mammalia. Structural modelling suggests that Gliap is an atypical mammalian type-I asparaginase inasmuch as it harbours the active centre of a type-I glycosylasparaginase but, like plant-type asparaginases, lacks their auto-proteolytic site and, in addition, exhibits significant type-II L-asparaginase enzymatic activity. Moreover, in contrast to glycosylasparaginases Gliap is enriched in the cytosolic fraction and not in lysosomes. The protein is particularly abundant in liver, testis and brain. In brain Gliap is exclusively expressed in astrocytes and prominently present in structures reminiscent of glial endfeet. These data suggest that Gliap is involved in astroglial production of the neuroactive amino acid L-aspartate.
authors.affiliation: AG Molecular Mechanisms of Plasticity, Department of Neurochemistry and Molecular Biology, Leibniz Institute for Neurobiology, Magdeburg, Germany.
authors.forename: Daniela C
authors.initials: DC
authors.lastname: Dieterich
authors.forename: Marco
authors.initials: M
authors.lastname: Landwehr
authors.forename: Carsten
authors.initials: C
authors.lastname: Reissner
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Smalla
authors.forename: Karin
authors.initials: K
authors.lastname: Richter
authors.forename: Gerald
authors.initials: G
authors.lastname: Wolf
authors.forename: Tobias M
authors.initials: TM
authors.lastname: Böckers
authors.forename: Eckart D
authors.initials: ED
authors.lastname: Gundelfinger
authors.forename: Michael R
authors.initials: MR
authors.lastname: Kreutz
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001215:Asparaginase / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics*; D001253:Astrocytes / Q000201:enzymology*; D001483:Base Sequence; D001921:Brain / Q000166:cytology / Q000201:enzymology*; D003001:Cloning, Molecular; D003600:Cytosol / Q000201:enzymology; D005982:Glutathione Transferase / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009928:Organ Specificity; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D011993:Recombinant Fusion Proteins; D005982:Glutathione Transferase; D001215:Asparaginase