8p0l | pdb_00008p0l
Crystal structure of human O-GlcNAcase in complex with an S-linked CKII peptide
Structural highlights
FunctionOGA_HUMAN Isoform 1: Cleaves GlcNAc but not GalNAc from O-glycosylated proteins. Can use p-nitrophenyl-beta-GlcNAc and 4-methylumbelliferone-GlcNAc as substrates but not p-nitrophenyl-beta-GalNAc or p-nitrophenyl-alpha-GlcNAc (in vitro) (PubMed:11148210). Does not bind acetyl-CoA and does not have histone acetyltransferase activity (PubMed:24088714).[1] [2] [3] [4] [5] Isoform 3: Cleaves GlcNAc but not GalNAc from O-glycosylated proteins. Can use p-nitrophenyl-beta-GlcNAc as substrate but not p-nitrophenyl-beta-GalNAc or p-nitrophenyl-alpha-GlcNAc (in vitro), but has about six times lower specific activity than isoform 1.[6] Publication Abstract from PubMedHuman O-linked beta-N-acetylglucosaminidase (hOGA) is one of the two enzymes involved in nuclear and cytoplasmic protein O-GlcNAcylation, an essential post-translational modification. The enzyme catalyzes the hydrolysis of the GlcNAc-O-(Ser/Thr) glycosidic bonds via anchimeric assistance through the 2-acetamido group of the GlcNAc sugar. However, the conformational itinerary of the GlcNAc ring during catalysis remains unclear. Here we report the crystal structure of wild type hOGA in complex with a nonhydrolyzable glycopeptide substrate and elucidate the full enzyme catalytic mechanism using QM/MM metadynamics. We show that the enzyme can bind the substrate in either a chair- or a boat-like conformation, but only the latter is catalytically competent, leading to the reaction products via (1,4)B/(1)S(3) --> [(4)E](double dagger) --> (4)C(1) and (4)C(1) --> [(4)E](double dagger) --> (1,4)B/(1)S(3) conformational itineraries for the first and second catalytic reaction steps, respectively. Our results reconcile previous experimental observations for human and bacterial OGA and will aid the development of more effective OGA inhibitors for diseases associated with impaired O-GlcNAcylation. Human O-GlcNAcase Uses a Preactivated Boat-skew Substrate Conformation for Catalysis. Evidence from X-ray Crystallography and QM/MM Metadynamics.,Calvelo M, Males A, Alteen MG, Willems LI, Vocadlo DJ, Davies GJ, Rovira C ACS Catal. 2023 Oct 10;13(20):13672-13678. doi: 10.1021/acscatal.3c02378. , eCollection 2023 Oct 20. PMID:37969138[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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