The Human Asparaginase-like Protein 1 hASRGL1 Is an Ntn Hydrolase with β-Aspartyl Peptidase Activity

Abstract

Herein we report the bacterial expression, purification, and enzymatic characterization of the human asparaginase-like protein 1 (hASRGL1). We present evidence that hASRGL1 exhibits β-aspartyl peptidase activity consistent with enzymes designated as plant-type asparaginases, which had thus far only been found in plants and bacteria. Similar to non-mammalian plant-type asparaginases, hASRGL1 is shown to be an Ntn hydrolase for which Thr168 serves as the essential N-terminal nucleophile for intramolecular processing and catalysis, corroborated in part by abolishment of both activities through the point-mutation Thr168Ala. In light of the activity profile reported here, ASRGL1s may act synergistically with protein L-isoaspartyl methyl transferase to relieve accumulation of potentially toxic isoaspartyl peptides in mammalian brain and other tissues.

Loss of ASRGL1 expression is an independent biomarker for disease-specific survival in endometrioid endometrial carcinoma

“…Here we have used an antibody against the isoaspartyl peptidase/ L-asparaginase protein ASRGL1, an enzyme involved in the production of L-aspartate [15,16] to assess its prognostic value in EC on two large tissue microarray (TMA) cohorts, together consisting of over 480 EC tumor samples. In a systematic search for novel EC biomarkers using The Human Protein Atlas [17][18][19], ASRGL1 was identified as a candidate biomarker based on differential expression in EC.…”

Intramolecular Cleavage of the hASRGL1 Homodimer Occurs in Two Stages

“…During this activation step, an acyl shift reaction occurs with the hydroxyl group of Thr168 attacking the carbonyl group of the preceding amino acid and forming an ester intermediate that is subsequently hydrolyzed to expose the N-terminal residue of the nascent β -subunit. 1 Once hASRGL1 is activated, its biological function is thought to be the clearing of isoaspartate-containing peptides that accumulate as a common source of nonenzymatic protein damage under physiological conditions. 2 Furthermore, the hASRGL1 asparaginase activity has generated interest in the therapeutic development of hASRGL1 as a potentially nonimmunogenic alternative to the bacterial asparaginases used to clinically treat acute lymphoblastic leukemia.…”

Human 60-kDa Lysophospholipase Contains an N-terminal l-Asparaginase Domain That Is Allosterically Regulated by l-Asparagine

“…A well characterized mammalian member of the Ntn nucleophile hydrolase superfamily is the human lysosomal aspartylgluco-saminidase, which catalyzes the hydrolysis of glucosylated L-Asn molecules generated during proteolytic breakdown of glycoproteins (13,14). The human genome encodes another enzyme of this Ntn hydrolase family, variably termed human asparaginase-like protein 1 (15), glial asparaginase (16), CRASH (17), or hASNase3 because its high homology with E. coli LASNase3 (encoded by the iaaA gene) (18). Crystal structures of the wild-type form and of a circular permutant version of hASNase3 have been reported recently (19 -22).…”