NUDIX hydrolase superfamily; NUDIX hydrolase is a superfamily of enzymes found in all three kingdoms of life, and it catalyzes the hydrolysis of NUcleoside DIphosphates linked to other moieties, X. Enzymes belonging to this superfamily require a divalent cation, such as Mg2+ or Mn2+ for their activity. Members of this family are recognized by a highly conserved 23-residue NUDIX motif (GX5EX7REUXEEXGU, where U = I, L or V), which forms a structural motif that functions as a metal binding and catalytic site. Substrates of NUDIX hydrolase include intact and oxidatively damaged nucleoside triphosphates, dinucleoside polyphosphates, nucleotide-sugars and dinucleotide enzymes. These substrates are metabolites or cell signaling molecules that require regulation during different stages of the cell cycle or during periods of stress. In general, the role of the NUDIX hydrolase is to sanitize the nucleotide pools and to maintain cell viability, thereby serving as surveillance and "house-cleaning" enzymes. Substrate specificity is used to define child families within the superfamily. Differences in substrate specificity are determined by the N-terminal extension or by residues in variable loop regions. Mechanistically, substrate hydrolysis occurs by a nucleophilic substitution reaction, with variation in the numbers and roles of divalent cations required. This superfamily consists of at least nine families: IPP (isopentenyl diphosphate) isomerase, ADP ribose pyrophosphatase, mutT pyrophosphohydrolase, coenzyme-A pyrophosphatase, MTH1-7,8-dihydro-8-oxoguanine-triphosphatase, diadenosine tetraphosphate hydrolase, NADH pyrophosphatase, GDP-mannose hydrolase and the c-terminal portion of the mutY adenine glycosylase.

                        10        20        30        40        50        60
                ....*....|....*....|....*....|....*....|....*....|....*....|
8DP8_B       13 AIAIVYrelsDGSQTVLLAKMKGLADEKGWMFVRGHVREDEeaDPGVAAIRETQEETGFT 72
Cdd:cd02883   3 VGAVVF----DDEGRVLLVRRSDGPGPGGWELPGGGVEPGE--TPEEAAVREVREETGLD 56

NUDIX hydrolase superfamily; NUDIX hydrolase is a superfamily of enzymes found in all three kingdoms of life, and it catalyzes the hydrolysis of NUcleoside DIphosphates linked to other moieties, X. Enzymes belonging to this superfamily require a divalent cation, such as Mg2+ or Mn2+ for their activity. Members of this family are recognized by a highly conserved 23-residue NUDIX motif (GX5EX7REUXEEXGU, where U = I, L or V), which forms a structural motif that functions as a metal binding and catalytic site. Substrates of NUDIX hydrolase include intact and oxidatively damaged nucleoside triphosphates, dinucleoside polyphosphates, nucleotide-sugars and dinucleotide enzymes. These substrates are metabolites or cell signaling molecules that require regulation during different stages of the cell cycle or during periods of stress. In general, the role of the NUDIX hydrolase is to sanitize the nucleotide pools and to maintain cell viability, thereby serving as surveillance and "house-cleaning" enzymes. Substrate specificity is used to define child families within the superfamily. Differences in substrate specificity are determined by the N-terminal extension or by residues in variable loop regions. Mechanistically, substrate hydrolysis occurs by a nucleophilic substitution reaction, with variation in the numbers and roles of divalent cations required. This superfamily consists of at least nine families: IPP (isopentenyl diphosphate) isomerase, ADP ribose pyrophosphatase, mutT pyrophosphohydrolase, coenzyme-A pyrophosphatase, MTH1-7,8-dihydro-8-oxoguanine-triphosphatase, diadenosine tetraphosphate hydrolase, NADH pyrophosphatase, GDP-mannose hydrolase and the c-terminal portion of the mutY adenine glycosylase.

                        10        20        30        40        50        60
                ....*....|....*....|....*....|....*....|....*....|....*....|
8DP8_B       13 AIAIVYrelsDGSQTVLLAKMKGLADEKGWMFVRGHVREDEeaDPGVAAIRETQEETGFT 72
Cdd:cd02883   3 VGAVVF----DDEGRVLLVRRSDGPGPGGWELPGGGVEPGE--TPEEAAVREVREETGLD 56

mRNA decapping enzyme 2; mRNA decapping enzyme 2 (Dcp2p; EC 3.6.1.62), nucleoside diphosphate linked moiety X))-type motif 20/Nudt20, is required for degradation of mRNAs, both in normal mRNA turnover, and in nonsense-mediated mRNA decay (NMD). Its catalytic subunit, and Dcp1p are the two components of the decapping enzyme complex. Decapping is a key step in both general and nonsense-mediated 5'->3' mRNA-decay pathways. Dcp2p contains an all-alpha helical N-terminal domain and a C-terminal domain which has the NUDIX fold. While decapping is not dependent on the N-terminus of Dcp2p, it does affect its efficiency. Dcp1p binds the N-terminal domain of Dcp2p stimulating the decapping activity of Dcp2p. Decapping permits the degradation of the transcript and is a site of numerous control inputs. It is responsible for nonsense-mediated decay as well as AU-rich element (ARE)-mediated decay. In addition, it may also play a role in the levels of mRNA. Enzymes belonging to the NUDIX hydrolase superfamily require a divalent cation, such as Mg2+ or Mn2+, for their activity and are recognized by a highly conserved 23-residue NUDIX motif (GX5EX7REUXEEXGU, where U = I, L or V).

                        10        20        30
                ....*....|....*....|....*....|..
8DP8_B       40 KGWMFVRGHVREDEeaDPGVAAIRETQEETGF 71
Cdd:cd03672  26 SSWGFPKGKINKDE--SDADCAIREVYEETGF 55

ADP-ribose pyrophosphatase YjhB, NUDIX family [Nucleotide transport and metabolism];

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
8DP8_B       13 AIAIVYRElsDGsqTVLLAKMKGLADEKGWMFVRGHVREDEeaDPGVAAIRETQEETGFTGmvkKSGAPFTQPGSKDTQR 92
Cdd:COG1051   9 VDAVIFRK--DG--RVLLVRRADEPGKGLWALPGGKVEPGE--TPEEAALRELREETGLEV---EVLELLGVFDHPDRGH 79

                        90       100       110
                ....*....|....*....|....*....|....*...
8DP8_B       93 VITiHPHIVQVQEASKSKDTEDTvkrQFLWVHPSEVRS 130
Cdd:COG1051  80 VVS-VAFLAEVLSGEPRADDEID---EARWFPLDELPE 113

translation initiation factor IF-2B alpha subunit; Eukaryotic translation initiation factor 2B subunit alpha (EIF2B1) is one of five subunits of eukaryotic translation initiation factor 2B (EIF2B), a GTP exchange factor for eukaryotic initiation factor 2 and an essential regulator for protein synthesis. Mutations in this gene and the genes encoding other EIF2B subunits have been associated with leukoencephalopathy with vanishing white matter. Members of the NUDIX hydrolase superfamily catalyze the hydrolysis of NUcleoside DIphosphates linked to other moieties, X. Enzymes belonging to this superfamily require a divalent cation, such as Mg2+ or Mn2+, for their activity and contain a highly conserved 23-residue NUDIX motif (GX5EX7REUXEEXGU, where U = I, L or V), which functions as a metal binding and catalytic site. Substrates of NUDIX hydrolases include intact and oxidatively damaged nucleoside triphosphates, dinucleoside polyphosphates, nucleotide-sugars and dinucleotide enzymes. These substrates are metabolites or cell signaling molecules that require regulation during different stages of the cell cycle or during periods of stress. In general, the role of the NUDIX hydrolase is to sanitize the nucleotide pools and to maintain cell viability, thereby serving as surveillance _ "house-cleaning" enzymes. Substrate specificity is used to define families within the superfamily. Differences in substrate specificity are determined by the N-terminal extension or by residues in variable loop regions. Mechanistically, substrate hydrolysis occurs by a nucleophilic substitution reaction, with variation in the numbers and roles of divalent cations required.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
8DP8_B       42 WMFVRGHVREDEeaDPGVAAIRETQEETGFTG----MVKKsGAPFTqpgSKDTQ--RVITIHPHIVQVQEASKSK-DTED 114
Cdd:cd18872  29 WAGISGSIESDD--PPLAAAWREIREETGLTPedveLLRQ-GKPFE---FTDESlgREWTVHPFLFRLKDDRAIKlDWEH 102

                        90
                ....*....|....*.
8DP8_B      115 TvkrQFLWVHPSEVRS 130
Cdd:cd18872 103 T---EWEWVDPTDILD 115

diadenosine 5',5'''-P1,P6-hexaphosphate hydrolase type 2 and similar proteins; Diadenosine 5',5'''-P1,P6-hexaphosphate hydrolase type 2 (DIPP2), also known as NUDIX (nucleoside diphosphate-linked moiety X)) motif 4; Nudt4, and other proteins including DIPP1/Nudt3, DIPP3a;APS2/Nudt10 and DIPP3beta;APS1/Nudt11. DIPP regulates the turnover of diphosphoinositol polyphosphates. The turnover of these high-energy diphosphoinositol polyphosphates represents a molecular switching activity with important regulatory consequences. Molecular switching by diphosphoinositol polyphosphates may contribute to regulating intracellular trafficking. Several alternatively spliced transcript variants have been described, but the full-length nature of some variants has not been determined. Isoforms DIPP2alpha and DIPP2beta are distinguishable from each other solely by DIPP2beta possessing one additional amino acid due to intron boundary skidding in alternate splicing. Members of the NUDIX hydrolase superfamily catalyze the hydrolysis of NUcleoside DIphosphates linked to other moieties, X. Enzymes belonging to this superfamily require a divalent cation, such as Mg2+ or Mn2+, for their activity and contain a highly conserved 23-residue NUDIX motif (GX5EX7REUXEEXGU, where U = I, L or V), which functions as a metal binding and catalytic site. Substrates of NUDIX hydrolases include intact and oxidatively damaged nucleoside triphosphates, dinucleoside polyphosphates, nucleotide-sugars and dinucleotide enzymes. These substrates are metabolites or cell signaling molecules that require regulation during different stages of the cell cycle or during periods of stress. In general, the role of the NUDIX hydrolase is to sanitize the nucleotide pools and to maintain cell viability, thereby serving as surveillance _ "house-cleaning" enzymes. Substrate specificity is used to define families within the superfamily. Differences in substrate specificity are determined by the N-terminal extension or by residues in variable loop regions. Mechanistically, substrate hydrolysis occurs by a nucleophilic substitution reaction, with variation in the numbers and roles of divalent cations required.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
8DP8_B       15 AIVYRELSDGSQtVLLAKMKglaDEKGWMFVRGHVREDEEadPGVAAIRETQEETGFTG-MVKKSGAPFTQPGSKDTQRV 93
Cdd:cd04666   5 ALPYRITKGELE-VLLITSR---KTGRWILPKGGPEKGET--PAEAAAREAWEEAGVRGkVLKRPLGVYRYRKRLKGRGL 78

                        90       100       110       120       130
                ....*....|....*....|....*....|....*....|....*....|..
8DP8_B       94 ITI-HPHIVQVQEAskSKDTEDTVKRQFLWVHPSEVRSKLQRAEMIQAWDQL 144
Cdd:cd04666  79 PCRvHVFPLEVTEE--LDDWPEKHERKRRWFSPEEAAELVDEPELRELLRRL 128

uncharacterized NUDIX hydrolase subfamily; NUDIX hydrolase is a superfamily of enzymes found in all three kingdoms of life, and it catalyzes the hydrolysis of NUcleoside DIphosphates linked to other moieties, X. Enzymes belonging to this superfamily require a divalent cation, such as Mg2+ or Mn2+ for their activity. Members of this family are recognized by a highly conserved 23-residue NUDIX motif (GX5EX7REUXEEXGU, where U = I, L or V), which forms a structural motif that functions as a metal binding and catalytic site. Substrates of NUDIX hydrolase include intact and oxidatively damaged nucleoside triphosphates, dinucleoside polyphosphates, nucleotide-sugars and dinucleotide enzymes. These substrates are metabolites or cell signaling molecules that require regulation during different stages of the cell cycle or during periods of stress. In general, the role of the NUDIX hydrolase is to sanitize the nucleotide pools and to maintain cell viability, thereby serving as surveillance and "house-cleaning" enzymes. Substrate specificity is used to define child families within the superfamily. Differences in substrate specificity are determined by the N-terminal extension or by residues in variable loop regions. Mechanistically, substrate hydrolysis occurs by a nucleophilic substitution reaction, with variation in the numbers and roles of divalent cations required. This superfamily consists of at least nine families: IPP (isopentenyl diphosphate) isomerase, ADP ribose pyrophosphatase, mutT pyrophosphohydrolase, coenzyme-A pyrophosphatase, MTH1-7,8-dihydro-8-oxoguanine-triphosphatase, diadenosine tetraphosphate hydrolase, NADH pyrophosphatase, GDP-mannose hydrolase and the c-terminal portion of the mutY adenine glycosylase.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
8DP8_B       18 YReLSDGSQTVLLAKMKG----LADEKGWMFVRGHVREDEeaDPGVAAIRETQEETGFTGmvkkSGA-----PFTQPGSK 88
Cdd:cd04662   8 YR-RRDGGLEVLLVHPGGpfwaRKDEGAWSIPKGEVEPGE--DPLAAARREFEEETGFPA----PGPfiplgEVRQKSGK 80

uncharacterized NUDIX hydrolase subfamily; NUDIX hydrolase is a superfamily of enzymes found in all three kingdoms of life, and it catalyzes the hydrolysis of NUcleoside DIphosphates linked to other moieties, X. Enzymes belonging to this superfamily require a divalent cation, such as Mg2+ or Mn2+ for their activity. Members of this family are recognized by a highly conserved 23-residue NUDIX motif (GX5EX7REUXEEXGU, where U = I, L or V), which forms a structural motif that functions as a metal binding and catalytic site. Substrates of NUDIX hydrolase include intact and oxidatively damaged nucleoside triphosphates, dinucleoside polyphosphates, nucleotide-sugars and dinucleotide enzymes. These substrates are metabolites or cell signaling molecules that require regulation during different stages of the cell cycle or during periods of stress. In general, the role of the NUDIX hydrolase is to sanitize the nucleotide pools and to maintain cell viability, thereby serving as surveillance and "house-cleaning" enzymes. Substrate specificity is used to define child families within the superfamily. Differences in substrate specificity are determined by the N-terminal extension or by residues in variable loop regions. Mechanistically, substrate hydrolysis occurs by a nucleophilic substitution reaction, with variation in the numbers and roles of divalent cations required. This superfamily consists of at least nine families: IPP (isopentenyl diphosphate) isomerase, ADP ribose pyrophosphatase, mutT pyrophosphohydrolase, coenzyme-A pyrophosphatase, MTH1-7,8-dihydro-8-oxoguanine-triphosphatase, diadenosine tetraphosphate hydrolase, NADH pyrophosphatase, GDP-mannose hydrolase and the c-terminal portion of the mutY adenine glycosylase.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
8DP8_B       13 AIAIVYrelsDGSQTVLLAkmkgLADEK------G-WMFVRGHVREDEeaDPGVAAIRETQEETGftgmVKKSGAPFTqp 85
Cdd:cd18882   4 AIAILY----DDRGKVLLQ----LRDDKpgipypGyWGLFGGHLEPGE--TPEEAIRRELEEEIG----YEPGEFRFF-- 67

                        90       100       110       120       130       140
                ....*....|....*....|....*....|....*....|....*....|....*....|....*.
8DP8_B       86 GSKDTQRVITIHPHIVQVQEAsksKDTEDTV---KRQFLWVHPSEVR---SKLQRAEMIQAWDQLH 145
Cdd:cd18882  68 LLYTEDDGEDRIRHVFHAPLD---VDLSDLVlneGQALRLFSPEEILqgpLYSNLAGILRPLLAIH 130

uncharacterized NUDIX hydrolase subfamily; NUDIX hydrolase is a superfamily of enzymes found in all three kingdoms of life, and it catalyzes the hydrolysis of NUcleoside DIphosphates linked to other moieties, X. Enzymes belonging to this superfamily require a divalent cation, such as Mg2+ or Mn2+ for their activity. Members of this family are recognized by a highly conserved 23-residue NUDIX motif (GX5EX7REUXEEXGU, where U = I, L or V), which forms a structural motif that functions as a metal binding and catalytic site. Substrates of NUDIX hydrolase include intact and oxidatively damaged nucleoside triphosphates, dinucleoside polyphosphates, nucleotide-sugars and dinucleotide enzymes. These substrates are metabolites or cell signaling molecules that require regulation during different stages of the cell cycle or during periods of stress. In general, the role of the NUDIX hydrolase is to sanitize the nucleotide pools and to maintain cell viability, thereby serving as surveillance and "house-cleaning" enzymes. Substrate specificity is used to define child families within the superfamily. Differences in substrate specificity are determined by the N-terminal extension or by residues in variable loop regions. Mechanistically, substrate hydrolysis occurs by a nucleophilic substitution reaction, with variation in the numbers and roles of divalent cations required. This superfamily consists of at least nine families: IPP (isopentenyl diphosphate) isomerase, ADP ribose pyrophosphatase, mutT pyrophosphohydrolase, coenzyme-A pyrophosphatase, MTH1-7,8-dihydro-8-oxoguanine-triphosphatase, diadenosine tetraphosphate hydrolase, NADH pyrophosphatase, GDP-mannose hydrolase and the c-terminal portion of the mutY adenine glycosylase.

                        10        20        30        40        50
                ....*....|....*....|....*....|....*....|....*....|..
8DP8_B       21 LSDGSQTVLLAKMKGLadeKGWMFVRGHVreDEEADPGVAAIRETQEETGFT 72
Cdd:cd03674   9 VNPDRGKVLLVHHRKL---GRWLQPGGHV--EPDEDPLEAALREAREETGLD 55

ADP-ribose pyrophosphatase and similar proteins; ADP-ribose pyrophosphatase (ADPRase; EC 3.6.1.13) catalyzes the hydrolysis of ADP-ribose to AMP and ribose-5-P. Like other members of the NUDIX hydrolase superfamily of enzymes, it is thought to require a divalent cation, such as Mg2+, for its activity. It also contains a 23-residue NUDIX motif (GX5EX7REUXEEXGU, where U = I, L or V) which functions as a metal binding site/catalytic site. In addition to the NUDIX motif, there are additional conserved amino acid residues, distal from the signature sequence, that correlate with substrate specificity. In humans, there are four distinct ADPRase activities, three putative cytosolic (ADPRase-I, -II, and -Mn) and a single mitochondrial enzyme (ADPRase-m). ADPRase-m is also known as NUDT9. It can be distinugished from the cytosolic ADPRase by a N-terminal target sequence unique to mitochondrial ADPRase. NUDT9 functions as a monomer.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....*....
8DP8_B       28 VLLAKMKGLADEKGWMFVRGHVREDEEADpgVAAIRETQEETGFTGMVK 76
Cdd:cd04691  14 VLLVKRAYGPGKGRWTLPGGFVEEGETLD--EAIVREVLEETGIDAKPV 60

dihydroneopterin hydrolase; DHNTP pyrophosphatase (DHNTPase) catalyzes the hydrolysis of dihydroneopterin triphosphate (DHNTP) to dihydroneopterin monophosphate (DHNMP) and pyrophosphate,the second step in the pterin branch of the folate synthesis pathway in bacteria. Members of the NUDIX hydrolase superfamily catalyze the hydrolysis of NUcleoside DIphosphates linked to other moieties, X. Enzymes belonging to this superfamily require a divalent cation, such as Mg2+ or Mn2+, for their activity and contain a highly conserved 23-residue NUDIX motif (GX5EX7REUXEEXGU, where U = I, L or V), which functions as a metal binding and catalytic site. Substrates of NUDIX hydrolases include intact and oxidatively damaged nucleoside triphosphates, dinucleoside polyphosphates, nucleotide-sugars and dinucleotide enzymes. These substrates are metabolites or cell signaling molecules that require regulation during different stages of the cell cycle or during periods of stress. In general, the role of the NUDIX hydrolase is to sanitize the nucleotide pools and to maintain cell viability, thereby serving as surveillance _ "house-cleaning" enzymes. Substrate specificity is used to define families within the superfamily. Differences in substrate specificity are determined by the N-terminal extension or by residues in variable loop regions. Mechanistically, substrate hydrolysis occurs by a nucleophilic substitution reaction, with variation in the numbers and roles of divalent cations required.

                        10        20        30        40        50        60
                ....*....|....*....|....*....|....*....|....*....|....*....|.
8DP8_B       15 AIVYRElSDGSQtVLLAKMkglADEKG-WMFVRGHVREDEeaDPGVAAIRETQEETGFTGM 74
Cdd:cd04664   5 VVIYRK-DEEGE-VLLLKR---TDDGGfWQSVTGGIEDGE--TPWQAALRELKEETGLDPL 58

ADP-ribose pyrophosphatase, UDP-glucose pyrophosphatase, and similar proteins; ADP-ribose pyrophosphatase (ADPRase) ( NUDIX (Nucleoside diphosphate-linked moiety X)) motif 5; Nudt5) catalyzes the hydrolysis of ADP-ribose and a variety of additional ADP-sugar conjugates to AMP and ribose-5-phosphate. In humans, there are four distinct ADPRase activities, three putative cytosolic enzymes (ADPRase-I, -II, and -Mn) and a single mitochondrial enzyme (ADPRase-m). Human ADPRase-II is also referred to as NUDT5. It lacks the N-terminal target sequence unique to mitochondrial ADPRase. The different cytosolic types are distinguished by their specificities for substrate and specific requirement for metal ions. NUDT5 forms a homodimer. It also contains a highly conserved 23-residue NUDIX motif (GX5EX7REUXEEXGU, where U = I, L or V) which functions as a metal binding site/catalytic site. In addition to the NUDIX motif, there are additional conserved amino acid residues, distal from the signature sequence, that correlate with substrate specificity. UDP-glucose pyrophosphatase (UGPPase) (EC 3.6.1.45; also known as nucleoside diphosphate-linked moiety X)) motif 14; Nudt14) hydrolyzes the pyrophosphate of the nucleoside diphosphate sugar to generate glucose-1-P and UMP. In mammals, UDP-glucose is the glucosyl donor for the synthesis of the storage polysaccharide glycogen. UGPPase, as a regulator of UDP-glucose, could play a regulatory role, but it has been shown to prefer ADP-ribose over UDP-glucose. Like other members of the NUDIX hydrolase superfamily, it requires a divalent cation, such as Mg2+, for its activity. It also contains a highly conserved 23-residue NUDIX motif (GX5EX7REUXEEXGU, where U = I, L or V) which functions as a metal binding site/catalytic site.

                        10        20        30        40
                ....*....|....*....|....*....|....*....|....
8DP8_B       44 FVRGHVREDEeaDPGVAAIRETQEETGFT-GMVKKSGAPFTQPG 86
Cdd:cd03424  33 LPAGKIDPGE--DPEEAARRELEEETGYTaGDLELLGSFYPSPG 74

GDP-mannose hydrolase (GDPMK), and similar proteins; GDP-mannose hydrolase (GDPMK) is a NUDIX enzyme that uses GDP-mannose as the preferred substrate. It is distinct from Nudix ADP-ribose hydrolases. GDPMK and ADP-ribose pyrophosphatase seem to use similar catalytic mechanism. However, GDPMK hydrolysis does not rely on a single glutamate as the catalytic base; rather, it is dependent on residues that coordinate the magnesium ions and residues that position the substrate properly for catalysis. Members of the NUDIX hydrolase superfamily catalyze the hydrolysis of NUcleoside DIphosphates linked to other moieties, X. Enzymes belonging to this superfamily require a divalent cation, such as Mg2+ or Mn2+, for their activity and contain a highly conserved 23-residue NUDIX motif (GX5EX7REUXEEXGU, where U = I, L or V), which functions as a metal binding and catalytic site. Substrates of NUDIX hydrolases include intact and oxidatively damaged nucleoside triphosphates, dinucleoside polyphosphates, nucleotide-sugars and dinucleotide enzymes. These substrates are metabolites or cell signaling molecules that require regulation during different stages of the cell cycle or during periods of stress. In general, the role of the NUDIX hydrolase is to sanitize the nucleotide pools and to maintain cell viability, thereby serving as surveillance _ "house-cleaning" enzymes. Substrate specificity is used to define families within the superfamily. Differences in substrate specificity are determined by the N-terminal extension or by residues in variable loop regions. Mechanistically, substrate hydrolysis occurs by a nucleophilic substitution reaction, with variation in the numbers and roles of divalent cations required.

                        10        20        30        40        50        60
                ....*....|....*....|....*....|....*....|....*....|....*....|..
8DP8_B       36 LADEKGWMF--VRGHVredEEADPGVAAIRETQEETGFT-GMVKKSGAPFTQPGSKdTQRVI 94
Cdd:cd24157  31 LGGGDGWLIeaCAGLL---DGDDPEDCIRREAEEETGYRlGDLEKVFTAYSSPGIV-TERIH 88