ID IUNH_CRIFA Reviewed; 315 AA. AC Q27546; DT 01-NOV-1997, integrated into UniProtKB/Swiss-Prot. DT 23-JAN-2007, sequence version 3. DT 27-MAR-2024, entry version 101. DE RecName: Full=Inosine-uridine preferring nucleoside hydrolase {ECO:0000303|PubMed:8634238}; DE Short=IU-NH {ECO:0000303|PubMed:8634238}; DE Short=IU-nucleoside hydrolase {ECO:0000303|PubMed:8634238}; DE EC=3.2.2.2 {ECO:0000269|PubMed:1939115}; DE EC=3.2.2.3 {ECO:0000269|PubMed:1939115}; DE AltName: Full=Non-specific nucleoside hydrolase {ECO:0000303|PubMed:1939115}; GN Name=IUNH; OS Crithidia fasciculata. OC Eukaryota; Discoba; Euglenozoa; Kinetoplastea; Metakinetoplastina; OC Trypanosomatida; Trypanosomatidae; Leishmaniinae; Crithidia. OX NCBI_TaxID=5656; RN [1] RP NUCLEOTIDE SEQUENCE [GENOMIC DNA], PARTIAL PROTEIN SEQUENCE, MASS RP SPECTROMETRY, AND MUTAGENESIS. RX PubMed=8634237; DOI=10.1021/bi952998u; RA Gopaul D.N., Meyer S.L., Degano M., Sacchettini J.C., Schramm V.L.; RT "Inosine-uridine nucleoside hydrolase from Crithidia fasciculata. Genetic RT characterization, crystallization, and identification of histidine 241 as a RT catalytic site residue."; RL Biochemistry 35:5963-5970(1996). RN [2] RP FUNCTION, CATALYTIC ACTIVITY, SUBSTRATE SPECIFICITY, BIOPHYSICOCHEMICAL RP PROPERTIES, SUBUNIT, AND PATHWAY. RX PubMed=1939115; DOI=10.1016/s0021-9258(18)54759-1; RA Parkin D.W., Horenstein B.A., Abdulah D.R., Estupinan B., Schramm V.L.; RT "Nucleoside hydrolase from Crithidia fasciculata. Metabolic role, RT purification, specificity, and kinetic mechanism."; RL J. Biol. Chem. 266:20658-20665(1991). RN [3] RP X-RAY CRYSTALLOGRAPHY (2.5 ANGSTROMS) IN COMPLEX WITH SUBSTRATE AND CALCIUM RP IONS, AND ACTIVE SITE. RX PubMed=8634238; DOI=10.1021/bi952999m; RA Degano M., Gopaul D.N., Scapin G., Schramm V.L., Sacchettini J.C.; RT "Three-dimensional structure of the inosine-uridine nucleoside N- RT ribohydrolase from Crithidia fasciculata."; RL Biochemistry 35:5971-5981(1996). CC -!- FUNCTION: Catalyzes the hydrolysis of the N-glycosidic bond of commonly CC occurring purine and pyrimidine nucleosides into ribose and the base, CC but has a preference for inosine and uridine as substrates. Is not CC active on thymidine and 2'-deoxynucleosides. Functions in purine CC salvage from the blood of the host, a fundamental pathway since CC protozoan parasites such as C.fasciculata are incapable of de novo CC purine biosynthesis. {ECO:0000269|PubMed:1939115}. CC -!- CATALYTIC ACTIVITY: CC Reaction=H2O + inosine = D-ribose + hypoxanthine; Xref=Rhea:RHEA:16657, CC ChEBI:CHEBI:15377, ChEBI:CHEBI:17368, ChEBI:CHEBI:17596, CC ChEBI:CHEBI:47013; EC=3.2.2.2; Evidence={ECO:0000269|PubMed:1939115}; CC -!- CATALYTIC ACTIVITY: CC Reaction=H2O + uridine = D-ribose + uracil; Xref=Rhea:RHEA:15577, CC ChEBI:CHEBI:15377, ChEBI:CHEBI:16704, ChEBI:CHEBI:17568, CC ChEBI:CHEBI:47013; EC=3.2.2.3; Evidence={ECO:0000269|PubMed:1939115}; CC -!- COFACTOR: CC Name=Ca(2+); Xref=ChEBI:CHEBI:29108; CC Evidence={ECO:0000250|UniProtKB:P83851}; CC -!- BIOPHYSICOCHEMICAL PROPERTIES: CC Kinetic parameters: CC KM=380 uM for inosine {ECO:0000269|PubMed:1939115}; CC KM=460 uM for adenosine {ECO:0000269|PubMed:1939115}; CC KM=420 uM for guanosine {ECO:0000269|PubMed:1939115}; CC KM=145 uM for purine riboside {ECO:0000269|PubMed:1939115}; CC KM=1300 uM for 5-methyluridine {ECO:0000269|PubMed:1939115}; CC KM=1220 uM for uridine {ECO:0000269|PubMed:1939115}; CC KM=4700 uM for cytosine {ECO:0000269|PubMed:1939115}; CC Vmax=50 umol/min/mg enzyme with inosine as substrate CC {ECO:0000269|PubMed:1939115}; CC Vmax=7.6 umol/min/mg enzyme with adenosine as substrate CC {ECO:0000269|PubMed:1939115}; CC Vmax=70 umol/min/mg enzyme with guanosine as substrate CC {ECO:0000269|PubMed:1939115}; CC Vmax=0.03 umol/min/mg enzyme with purine riboside as substrate CC {ECO:0000269|PubMed:1939115}; CC Vmax=380 umol/min/mg enzyme with 5-methyluridine as substrate CC {ECO:0000269|PubMed:1939115}; CC Vmax=255 umol/min/mg enzyme with uridine as substrate CC {ECO:0000269|PubMed:1939115}; CC Vmax=36 umol/min/mg enzyme with cytosine as substrate CC {ECO:0000269|PubMed:1939115}; CC Note=kcat is 32 sec(-1) with inosine as substrate. kcat is 243 CC sec(-1) with 5-methyluridine as substrate. CC {ECO:0000269|PubMed:1939115}; CC -!- PATHWAY: Purine metabolism; purine nucleoside salvage. CC {ECO:0000305|PubMed:1939115}. CC -!- SUBUNIT: Homotetramer. {ECO:0000269|PubMed:1939115}. CC -!- MASS SPECTROMETRY: Mass=34194; Mass_error=4; Method=Electrospray; CC Evidence={ECO:0000269|PubMed:8634237}; CC -!- SIMILARITY: Belongs to the IUNH family. {ECO:0000305}. CC --------------------------------------------------------------------------- CC Copyrighted by the UniProt Consortium, see https://www.uniprot.org/terms CC Distributed under the Creative Commons Attribution (CC BY 4.0) License CC --------------------------------------------------------------------------- DR EMBL; U43371; AAC47119.1; -; Genomic_DNA. DR PDB; 1MAS; X-ray; 2.50 A; A/B=3-315. DR PDB; 2MAS; X-ray; 2.30 A; A/B/C/D=3-315. DR PDBsum; 1MAS; -. DR PDBsum; 2MAS; -. DR AlphaFoldDB; Q27546; -. DR SMR; Q27546; -. DR BindingDB; Q27546; -. DR ChEMBL; CHEMBL3826862; -. DR KEGG; ag:AAC47119; -. DR VEuPathDB; TriTrypDB:CFAC1_140027700; -. DR BRENDA; 3.2.2.3; 1365. DR UniPathway; UPA00606; -. DR EvolutionaryTrace; Q27546; -. DR GO; GO:0047724; F:inosine nucleosidase activity; IEA:UniProtKB-EC. DR GO; GO:0046872; F:metal ion binding; IEA:UniProtKB-KW. DR GO; GO:0045437; F:uridine nucleosidase activity; IEA:UniProtKB-EC. DR GO; GO:0009117; P:nucleotide metabolic process; IEA:UniProtKB-KW. DR GO; GO:1901564; P:organonitrogen compound metabolic process; IEA:UniProt. DR CDD; cd02651; nuc_hydro_IU_UC_XIUA; 1. DR Gene3D; 3.90.245.10; Ribonucleoside hydrolase-like; 1. DR InterPro; IPR015910; I/U_nuclsd_hydro_CS. DR InterPro; IPR001910; Inosine/uridine_hydrolase_dom. DR InterPro; IPR023186; IUNH. DR InterPro; IPR036452; Ribo_hydro-like. DR PANTHER; PTHR12304; INOSINE-URIDINE PREFERRING NUCLEOSIDE HYDROLASE; 1. DR PANTHER; PTHR12304:SF4; IU_NUC_HYDRO DOMAIN-CONTAINING PROTEIN; 1. DR Pfam; PF01156; IU_nuc_hydro; 1. DR SUPFAM; SSF53590; Nucleoside hydrolase; 1. DR PROSITE; PS01247; IUNH; 1. PE 1: Evidence at protein level; KW 3D-structure; Calcium; Direct protein sequencing; Glycosidase; Hydrolase; KW Metal-binding; Nucleotide metabolism. FT INIT_MET 1 FT /note="Removed" FT CHAIN 2..315 FT /note="Inosine-uridine preferring nucleoside hydrolase" FT /id="PRO_0000206810" FT ACT_SITE 241 FT /note="Proton donor" FT /evidence="ECO:0000305|PubMed:8634238" FT BINDING 10 FT /ligand="Ca(2+)" FT /ligand_id="ChEBI:CHEBI:29108" FT BINDING 14 FT /ligand="substrate" FT /evidence="ECO:0000269|PubMed:8634238" FT BINDING 15 FT /ligand="Ca(2+)" FT /ligand_id="ChEBI:CHEBI:29108" FT BINDING 126 FT /ligand="Ca(2+)" FT /ligand_id="ChEBI:CHEBI:29108" FT BINDING 160 FT /ligand="substrate" FT /evidence="ECO:0000269|PubMed:8634238" FT BINDING 166 FT /ligand="substrate" FT /evidence="ECO:0000269|PubMed:8634238" FT BINDING 168 FT /ligand="substrate" FT /evidence="ECO:0000269|PubMed:8634238" FT BINDING 242 FT /ligand="Ca(2+)" FT /ligand_id="ChEBI:CHEBI:29108" FT MUTAGEN 241 FT /note="H->A: Loss of activity." FT /evidence="ECO:0000269|PubMed:8634237" FT STRAND 3..9 FT /evidence="ECO:0007829|PDB:2MAS" FT HELIX 13..24 FT /evidence="ECO:0007829|PDB:2MAS" FT STRAND 28..35 FT /evidence="ECO:0007829|PDB:2MAS" FT STRAND 37..40 FT /evidence="ECO:0007829|PDB:2MAS" FT HELIX 42..55 FT /evidence="ECO:0007829|PDB:2MAS" FT STRAND 63..65 FT /evidence="ECO:0007829|PDB:2MAS" FT STRAND 71..73 FT /evidence="ECO:0007829|PDB:2MAS" FT HELIX 79..82 FT /evidence="ECO:0007829|PDB:2MAS" FT STRAND 84..87 FT /evidence="ECO:0007829|PDB:2MAS" FT HELIX 105..115 FT /evidence="ECO:0007829|PDB:2MAS" FT STRAND 121..125 FT /evidence="ECO:0007829|PDB:2MAS" FT HELIX 130..138 FT /evidence="ECO:0007829|PDB:2MAS" FT HELIX 142..145 FT /evidence="ECO:0007829|PDB:2MAS" FT STRAND 148..152 FT /evidence="ECO:0007829|PDB:2MAS" FT STRAND 160..164 FT /evidence="ECO:0007829|PDB:2MAS" FT HELIX 167..170 FT /evidence="ECO:0007829|PDB:2MAS" FT HELIX 173..181 FT /evidence="ECO:0007829|PDB:2MAS" FT STRAND 182..184 FT /evidence="ECO:0007829|PDB:2MAS" FT STRAND 186..189 FT /evidence="ECO:0007829|PDB:2MAS" FT HELIX 191..194 FT /evidence="ECO:0007829|PDB:2MAS" FT HELIX 201..208 FT /evidence="ECO:0007829|PDB:2MAS" FT HELIX 213..230 FT /evidence="ECO:0007829|PDB:2MAS" FT STRAND 236..239 FT /evidence="ECO:0007829|PDB:2MAS" FT HELIX 242..250 FT /evidence="ECO:0007829|PDB:2MAS" FT HELIX 252..254 FT /evidence="ECO:0007829|PDB:2MAS" FT STRAND 255..259 FT /evidence="ECO:0007829|PDB:2MAS" FT STRAND 262..264 FT /evidence="ECO:0007829|PDB:2MAS" FT TURN 269..273 FT /evidence="ECO:0007829|PDB:1MAS" FT STRAND 275..277 FT /evidence="ECO:0007829|PDB:2MAS" FT STRAND 288..295 FT /evidence="ECO:0007829|PDB:2MAS" FT HELIX 297..311 FT /evidence="ECO:0007829|PDB:2MAS" SQ SEQUENCE 315 AA; 34326 MW; B88CF9DA41B53F43 CRC64; MPKKIILDCD PGLDDAVAIL LAHGNPEIEL LAITTVVGNQ TLAKVTRNAQ LVADIAGITG VPIAAGCDKP LVRKIMTAGH IHGESGMGTV AYPAEFKNKV DERHAVNLII DLVMSHEPKT ITLVPTGGLT NIAMAARLEP RIVDRVKEVV LMGGGYHEGN ATSVAEFNII IDPEAAHIVF NESWQVTMVG LDLTHQALAT PPILQRVKEV DTNPARFMLE IMDYYTKIYQ SNRYMAAAAV HDPCAVAYVI DPSVMTTERV PVDIELTGKL TLGMTVADFR NPRPEHCHTQ VAVKLDFEKF WGLVLDALER IGDPQ //