{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nO‐GlcNAcase (OGA) is the sole enzyme responsible for the removal of O‐linked N‑acetylglucosamine from serine and threonine residues of intracellular proteins, thereby dynamically regulating diverse signaling pathways much like phosphorylation. Initial cloning and characterization of human brain OGA established its biochemical properties, including its pH optimum, substrate selectivity for GlcNAc over similar sugars, and predominant cytoplasmic localization (1). Detailed kinetic and mechanistic studies have further demonstrated that OGA’s catalytic efficiency is driven largely by recognition of the GlcNAc moiety, independent of the peptide context, as evidenced by invariant kcat/Km values across a spectrum of substrates (3, 4). High‐resolution structural analyses, including crystal structures of truncated OGA, revealed an unusual arm‐in‐arm dimer formation with a conserved substrate‐binding cleft that accommodates glycopeptide substrates in a bidirectional yet conserved manner (13, 14, 15). Moreover, studies using chemically modified, S‐linked GlcNAc analogues have confirmed that such surrogates are enzymatically stable proxies for O‑GlcNAc, thereby underscoring the precision of OGA’s glycoside hydrolase activity."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "6"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nAltered expression or activity of OGA has been implicated in several human pathologies. In various cancers, decreased levels of MGEA5 transcripts—the gene encoding OGA—correlate with higher tumor grade and poor differentiation, and chromosomal rearrangements involving MGEA5 have been observed in certain soft tissue neoplasms (2, 5, 6, 10). In colorectal and bladder carcinomas, dysregulation of OGA (including its knockdown) is associated with increased global O‑GlcNAcylation, which in turn influences cell morphology, adhesion, and metastatic potential (8, 9). Furthermore, OGA’s modulation of cellular metabolism is highlighted by its ability to regulate aerobic glycolysis via inhibition of pyruvate kinase M2, thereby promoting tumor growth (11). In the cardiovascular context, microRNA‑mediated suppression of OGA (for example, by miR‑539) contributes to increased O‑GlcNAcylation in failing hearts, linking OGA activity to adaptive responses in heart failure (12)."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "7", "end_ref": "14"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nBeyond its roles in cancer and metabolism, OGA is critical in diverse cellular processes and disease contexts. In hematopoietic and leukemic systems, modulation of O‑GlcNAc cycling—including OGA activity—affects the balance between stem cell self‑renewal and differentiation, contributing to acute myeloid leukemia pathogenesis (16, 18, 19). In endothelial cells, conditions such as nucleoside diphosphate kinase‑B deficiency suppress OGA activity, leading to enhanced O‑GlcNAcylation and consequent vascular dysfunction in diabetes (16). Furthermore, OGA is implicated in gene regulatory mechanisms; for example, its recruitment to promoter regions facilitates assembly of repressor complexes that fine‑tune gamma‑globin gene expression (18). In the context of DNA damage repair, OGA is targeted to lesion sites to mediate deglycosylation, thereby contributing to efficient repair processes (20). Notably, pharmacological inhibition of OGA—using agents that increase O‑GlcNAc levels—has been shown to reduce the cellular uptake of pathogenic α‑synuclein fibrils, suggesting potential neuroprotective benefits in Parkinson’s disease, while viral oncoproteins such as HTLV‑1 Tax directly interact with and inhibit OGA to modulate viral transcription (21, 22)."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "15", "end_ref": "20"}]}, {"type": "t", "text": "\n"}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Y Gao, L Wells, F I Comer, et al. 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