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Literature summary extracted from

  • Wierzchowski, J.; Stachelska-Wierzchowska, A.; Wielgus-Kutrowska, B.; Bzowska, A.
    1,N6-ethenoadenine and other fluorescent nucleobase analogs as substrates for purine-nucleoside phosphorylases Spectroscopic and kinetic studies (2017), Curr. Pharm. Des., 23, 6948-6966 .
    View publication on PubMed

Application

EC Number Application Comment Organism
2.4.2.1 drug development the enzyme is a target for drug development Helicobacter pylori
2.4.2.1 drug development differences in specificity between homotrimeric (including human enzyme) and homohexameric PNPs, including various pathogenic organisms, make them interesting potential drug targets Bos taurus
2.4.2.1 drug development differences in specificity between homotrimeric (including human enzyme) and homohexameric PNPs, including various pathogenic organisms, make them interesting potential drug targets Escherichia coli
2.4.2.1 drug development differences in specificity between homotrimeric (including human enzyme) and homohexameric PNPs, including various pathogenic organisms, make them interesting potential drug targets Homo sapiens
2.4.2.1 drug development the enzyme is a target for development of anti-malarial drugs Plasmodium falciparum
2.4.2.1 pharmacology substrate 6-mercaptopurine-2'-deoxyriboside is of special interest, because, in contrast to a nucleoside, its parent purine is highly cytotoxic and is known as one of the first compounds applied as anti-cancer drugs Escherichia coli

Protein Variants

EC Number Protein Variants Comment Organism
2.4.2.1 N243D site-directed mutagenesis, the mutation in trimeric PNP changes the substrate specificity, making 6-aminopurine nucleosides good substrates Thermus thermophilus
2.4.2.1 N243D site-directed mutagenesis, the mutation in trimeric PNP changes the substrate specificity, making 6-aminopurine nucleosides good substrates Bos taurus
2.4.2.1 N243D site-directed mutagenesis, the mutation in trimeric PNP changes the substrate specificity, making 6-aminopurine nucleosides good substrates Homo sapiens

Inhibitors

EC Number Inhibitors Comment Organism Structure
2.4.2.1 6-methylformycin A strng inhibition Escherichia coli
2.4.2.1 9-(3-pyridylmethyl)-9-deaza-guanosine i.e. peldesine or BCX34 Bos taurus
2.4.2.1 9-(3-pyridylmethyl)-9-deaza-guanosine i.e. peldesine or BCX34 Homo sapiens
2.4.2.1 DADMe-immucillin-G i.e. forodesine or BCX4945 Bos taurus
2.4.2.1 DADMe-immucillin-G i.e. forodesine or BCX4945 Homo sapiens
2.4.2.1 DADMe-immucillin-G i.e. forodesine or BCX4945 Plasmodium falciparum
2.4.2.1 DADMe-immucillin-H i.e. ulodesine or BCX4208 Bos taurus
2.4.2.1 DADMe-immucillin-H i.e. ulodesine or BCX4208 Homo sapiens
2.4.2.1 DADMe-immucillin-H i.e. ulodesine or BCX4208 Plasmodium falciparum
2.4.2.1 DATMe-immucillin-H
-
 Bos taurus
2.4.2.1 DATMe-immucillin-H
-
 Homo sapiens
2.4.2.1 DFPP-DG
-
 Bos taurus
2.4.2.1 DFPP-DG
-
 Homo sapiens
2.4.2.1 Formycin A an analogue of adenosine Bos taurus
2.4.2.1 Formycin A
-
 Escherichia coli
2.4.2.1 Formycin A an analogue of adenosine Homo sapiens
2.4.2.1 formycin B structural, 9-deaza-8-aza analogue of inosine Bos taurus
2.4.2.1 formycin B structural, 9-deaza-8-aza analogue of inosine Escherichia coli
2.4.2.1 formycin B structural, 9-deaza-8-aza analogue of inosine Homo sapiens
2.4.2.1 immucillin-G an analogue of guanosine Bos taurus
2.4.2.1 immucillin-G an analogue of guanosine Homo sapiens
2.4.2.1 immucillin-H i.e. forodesine or BCX1777, an analogue of inosine Bos taurus
2.4.2.1 immucillin-H i.e. forodesine or BCX1777, an analogue of inosine Homo sapiens
2.4.2.1 additional information formycins are 9-deaza-8-aza-nucleosides and selective inhibitors of hexameric PNPs. 8-Aza-9-deazapurine derivatives as enzyme inhibitors, overview Escherichia coli
2.4.2.1 additional information immucillins are potent slow-binding inhibitors, forming rapidly the enzyme/inhibitor collision complex that is characterized by nM enzyme/inhibitor affinity, followed by a slow conformational change leading a tight-binding enzyme/inhibitor complex. Immucilins, like ground-state analogue inhibitors, bind with the stoichiometry of three molecules per enzyme trimer. Another interesting class of PNP inhibitors comprises so-called bisubstrate analogs, represented by purine-alkylphosphonates and difluoromethylene phosphonates, which compete with both PNP substrates, nucleoside and phosphate, and therefore interact with PNP with inhibition constants markedly dependent on inorganic phosphate concentration. 8-aza-9-deazapurine derivatives as enzyme inhibitors, overview Homo sapiens
2.4.2.1 SerMe-immucillin-H SerMe-ImmH, uses achiral dihydroxyaminoalcohol seramide as the ribocation mimic Bos taurus
2.4.2.1 SerMe-immucillin-H SerMe-ImmH, uses achiral dihydroxyaminoalcohol seramide as the ribocation mimic Homo sapiens

Natural Substrates/ Products (Substrates)

EC Number Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
2.4.2.1 1-methyladenosine + phosphate Escherichia coli
-
 1-methyladenine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 1-methylguanosine + phosphate Escherichia coli
-
 1-methylguanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 6-mercaptopurine-2'-deoxyriboside + phosphate Escherichia coli
-
 6-mercaptopurine + 2-deoxy-alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 8-azaguanine + alpha-D-ribose 1-phosphate Escherichia coli
-
 8-azaguanosine + phosphate
-
 r
2.4.2.1 8-azaguanosine + phosphate Escherichia coli
-
 8-azaguanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 8-azaguanosine + phosphate Homo sapiens
-
 8-azaguanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 9-beta-D-arabinosyl-2-fluoroadenine + phosphate Escherichia coli i.e. fludarabine 2-fluoroadenine + beta-D-arabinose 1-phosphate
-
 r
2.4.2.1 adenosine + phosphate Escherichia coli
-
 adenine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 guanosine + phosphate Thermus thermophilus
-
 guanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 guanosine + phosphate Bacillus cereus
-
 guanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 guanosine + phosphate Pectobacterium carotovorum
-
 guanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 guanosine + phosphate Plasmodium lophurae
-
 guanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 guanosine + phosphate Cellulomonas sp.
-
 guanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 guanosine + phosphate Bos taurus
-
 guanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 guanosine + phosphate Escherichia coli
-
 guanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 guanosine + phosphate Plasmodium falciparum
-
 guanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 guanosine + phosphate Homo sapiens
-
 guanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 guanosine + phosphate Helicobacter pylori
-
 guanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 inosine + phosphate Thermus thermophilus
-
 hypoxanthine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 inosine + phosphate Bacillus cereus
-
 hypoxanthine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 inosine + phosphate Pectobacterium carotovorum
-
 hypoxanthine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 inosine + phosphate Plasmodium lophurae
-
 hypoxanthine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 inosine + phosphate Cellulomonas sp.
-
 hypoxanthine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 inosine + phosphate Bos taurus
-
 hypoxanthine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 inosine + phosphate Escherichia coli
-
 hypoxanthine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 inosine + phosphate Plasmodium falciparum
-
 hypoxanthine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 inosine + phosphate Homo sapiens
-
 hypoxanthine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 inosine + phosphate Helicobacter pylori
-
 hypoxanthine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 nicotinamide riboside + phosphate Escherichia coli
-
 nicotinamide + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 xanthosine + phosphate Escherichia coli
-
 xanthine + alpha-D-ribose 1-phosphate
-
 r

Organism

EC Number Organism UniProt Comment Textmining
2.4.2.1 Bacillus cereus
-
-
-
2.4.2.1 Bos taurus P55859 calf
-
2.4.2.1 Cellulomonas sp. P81989
-
-
2.4.2.1 Escherichia coli P0ABP8
-
-
2.4.2.1 Escherichia coli P45563
-
-
2.4.2.1 Helicobacter pylori A0A518Y5Z2 multifunctional fusion protein
-
2.4.2.1 Homo sapiens P00941
-
-
2.4.2.1 Pectobacterium carotovorum
-
-
-
2.4.2.1 Plasmodium falciparum Q8I3X4
-
-
2.4.2.1 Plasmodium lophurae
-
-
-
2.4.2.1 Thermus thermophilus
-
-
-

Reaction

EC Number Reaction Comment Organism Reaction ID
2.4.2.1 purine ribonucleoside + phosphate = purine + alpha-D-ribose 1-phosphate molecular mechanism of catalysis involving protonation of the purine ring position N7, open and closed active site conformations, overview Escherichia coli
a
2.4.2.1 purine ribonucleoside + phosphate = purine + alpha-D-ribose 1-phosphate the trimeric PNPs show that there is no acidic residue in the vicinity of the purine ring N7, only the side-chain of Asn243 (Asn246 in Cellulomonas PNP) is found there. Moreover, in the latter structure, Asn246 interacts with purine through a water molecule, questioning the protonation mechanism in the catalysis. The molecular mechanism of catalysis of trimeric PNPs involves either protonation of the purine ring N7, or a negatively charged purine intermediate stabilized by hydrogen bonds of purine N(7) with Asn243, or of the purine N1H with Glu201 (Glu204 in Cellulomonas PNP). Ordered water molecules provide a proton transfer bridge to O6 and N7 and permit reversible formation of these hydrogen bonds. The alternative mechanism assumes a negatively charged purine ring in the transition state stabilized by a hydrogen bond from Asn243 to purine ring N7. Key catalytic role of Glu204 Cellulomonas sp.
a
2.4.2.1 purine ribonucleoside + phosphate = purine + alpha-D-ribose 1-phosphate the trimeric PNPs show that there is no acidic residue in the vicinity of the purine ring N7, only the side-chain of Asn243 is found there. The molecular mechanism of catalysis of trimeric PNPs involves either protonation of the purine ring N7, or a negatively charged purine intermediate stabilized by hydrogen bonds of purine N(7) with Asn243, or of the purine N1H with Glu201. Ordered water molecules provide a proton transfer bridge to O6 and N7 and permit reversible formation of these hydrogen bonds. The alternative mechanism assumes a negatively charged purine ring in the transition state stabilized by a hydrogen bond from Asn243 to purine ring N7. Key catalytic role of Glu201 Bos taurus
a
2.4.2.1 purine ribonucleoside + phosphate = purine + alpha-D-ribose 1-phosphate the trimeric PNPs show that there is no acidic residue in the vicinity of the purine ring N7, only the side-chain of Asn243 is found there. The molecular mechanism of catalysis of trimeric PNPs involves either protonation of the purine ring N7, or a negatively charged purine intermediate stabilized by hydrogen bonds of purine N(7) with Asn243, or of the purine N1H with Glu201. Ordered water molecules provide a proton transfer bridge to O6 and N7 and permit reversible formation of these hydrogen bonds. The alternative mechanism assumes a negatively charged purine ring in the transition state stabilized by a hydrogen bond from Asn243 to purine ring N7. Key catalytic role of Glu201 Homo sapiens
a

Source Tissue

EC Number Source Tissue Comment Organism Textmining
2.4.2.1 blood high PNP level Homo sapiens
-
2.4.2.1 erythrocyte
-
 Homo sapiens
-

Substrates and Products (Substrate)

EC Number Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
2.4.2.1 1,N6-ethenoadenosine + phosphate i.e. 3-beta-D-ribosylimidazo[2,l-i]purine Escherichia coli 1,N6-ethenoadenine + beta-D-ribose 1-phosphate
-
 r
2.4.2.1 1-methyladenosine + phosphate
-
 Escherichia coli 1-methyladenine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 1-methylguanosine + phosphate
-
 Escherichia coli 1-methylguanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 2,6-diamino-8-azapurine + alpha-D-ribose 1-phosphate PNP mutant D204N Bos taurus N7-D-ribosyl-2,6-diamino-8-azapurine + phosphate
-
 r
2.4.2.1 2,6-diamino-8-azapurine + alpha-D-ribose 1-phosphate
-
 Bos taurus N8-D-ribosyl-2,6-diamino-8-azapurine + phosphate
-
 r
2.4.2.1 2,6-diamino-8-azapurine + alpha-D-ribose 1-phosphate PNP mutant D204N Bos taurus N9-D-ribosyl-2,6-diamino-8-azapurine + phosphate
-
 r
2.4.2.1 6-mercaptopurine-2'-deoxyriboside + phosphate
-
 Escherichia coli 6-mercaptopurine + 2-deoxy-alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 8-azaguanine + alpha-D-ribose 1-phosphate
-
 Escherichia coli 8-azaguanosine + phosphate
-
 r
2.4.2.1 8-azaguanosine + phosphate
-
 Escherichia coli 8-azaguanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 8-azaguanosine + phosphate
-
 Homo sapiens 8-azaguanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 9-beta-D-arabinosyl-2-fluoroadenine + phosphate i.e. fludarabine Escherichia coli 2-fluoroadenine + beta-D-arabinose 1-phosphate
-
 r
2.4.2.1 adenosine + phosphate
-
 Escherichia coli adenine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 guanosine + phosphate
-
 Thermus thermophilus guanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 guanosine + phosphate
-
 Bacillus cereus guanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 guanosine + phosphate
-
 Pectobacterium carotovorum guanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 guanosine + phosphate
-
 Plasmodium lophurae guanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 guanosine + phosphate
-
 Cellulomonas sp. guanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 guanosine + phosphate
-
 Bos taurus guanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 guanosine + phosphate
-
 Escherichia coli guanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 guanosine + phosphate
-
 Plasmodium falciparum guanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 guanosine + phosphate
-
 Homo sapiens guanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 guanosine + phosphate
-
 Helicobacter pylori guanine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 inosine + phosphate
-
 Thermus thermophilus hypoxanthine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 inosine + phosphate
-
 Bacillus cereus hypoxanthine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 inosine + phosphate
-
 Pectobacterium carotovorum hypoxanthine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 inosine + phosphate
-
 Plasmodium lophurae hypoxanthine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 inosine + phosphate
-
 Cellulomonas sp. hypoxanthine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 inosine + phosphate
-
 Bos taurus hypoxanthine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 inosine + phosphate
-
 Escherichia coli hypoxanthine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 inosine + phosphate
-
 Plasmodium falciparum hypoxanthine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 inosine + phosphate
-
 Homo sapiens hypoxanthine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 inosine + phosphate
-
 Helicobacter pylori hypoxanthine + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 additional information hexameric PNPs accept as substrates many nucleoside analogues with various modifications in the purine ring, with an important exception of 7-deaza nucleosides. N7-Methylated guanosine, inosine and adenosine are unusual fluorescent substrates of both trimeric and hexameric PNPs Escherichia coli ?
-
-
2.4.2.1 additional information N1-methylated guanosine, inosine, and adenosine derivatives are selective substrates for hexameric PNP from Escherichia coli. Hexameric PNPs accept as substrates many nucleoside analogues with various modifications in the purine ring, with an important exception of 7-deaza nucleosides. N7-Methylated guanosine, inosine and adenosine are unusual fluorescent substrates of both trimeric and hexameric PNPs. Escherichia coli PNP converts pro-drugs, which are relative nontoxic purine nucleosides (for example 6-methyl purine 2'-deoxynucleoside or fludarabine), to their respective purine analogs (here, to 6-methylpurine and 2-fluoroadenine, respectively), which are very potent, toxic drugs. Enzymatic ribosylation of 8-azapurines, overview. Isoadenosine (3-beta-D-ribosyl-adenine), is, unlike the parent adenosine, a quite good substrate for mammalian and bacterial PNP. Ribosylation of tri-cyclic nucleobase analogues and phosphorolysis Escherichia coli ?
-
-
2.4.2.1 additional information nicotinamide riboside is a substrate of trimeric PNPs because it mimics 6-keto/N1H arrangement of 6-oxopurine nucleosides and 8-azaguanine. For trimeric PNP, the proton at the purine position N1 is required for catalysis. N7-Methylated guanosine, inosine and adenosine are unusual fluorescent substrates of both trimeric and hexameric PNPs. No activity with pro-drugs 6-methyl purine 2'-deoxynucleoside or fludarabine (9-beta-D-arabinosyl-2-fluoroadenine). Enzymatic ribosylation of 8-azapurines, overview. Isoadenosine (3-beta-D-ribosyl-adenine), is, unlike the parent adenosine, a quite good substrate for mammalian and bacterial PNP. Ribosylation of tri-cyclic nucleobase analogues and phosphorolysis Homo sapiens ?
-
-
2.4.2.1 additional information the hexamric PNP binds adenosine but it does not catalyze its phosphorolysis Thermus thermophilus ?
-
-
2.4.2.1 additional information the trimeric PNP binds adenosine but it does not catalyze its phosphorolysis Cellulomonas sp. ?
-
-
2.4.2.1 nicotinamide riboside + phosphate
-
 Escherichia coli nicotinamide + alpha-D-ribose 1-phosphate
-
 r
2.4.2.1 xanthosine + phosphate
-
 Escherichia coli xanthine + alpha-D-ribose 1-phosphate
-
 r

Subunits

EC Number Subunits Comment Organism
2.4.2.1 homodimer the enzyme is an exception since PNPs are almost all homotrimers or homohexamers Pectobacterium carotovorum
2.4.2.1 homohexamer
-
 Escherichia coli
2.4.2.1 homohexamer trimer of dimers Escherichia coli
2.4.2.1 homopentamer the enzyme is an exception since PNPs are almost all homotrimers or homohexamers Plasmodium lophurae
2.4.2.1 homotetramer the enzyme is an exception since PNPs are almost all homotrimers or homohexamers Bacillus cereus
2.4.2.1 homotrimer
-
 Bos taurus
2.4.2.1 homotrimer
-
 Homo sapiens
2.4.2.1 homotrimer or homohexamer the hexamer is a trimer of dimers Thermus thermophilus
2.4.2.1 homotrimer or homohexamer the hexamer is a trimer of dimers Cellulomonas sp.

Synonyms

EC Number Synonyms Comment Organism
2.4.2.1 DeoD
-
 Escherichia coli
2.4.2.1 PNP
-
 Thermus thermophilus
2.4.2.1 PNP
-
 Bacillus cereus
2.4.2.1 PNP
-
 Pectobacterium carotovorum
2.4.2.1 PNP
-
 Plasmodium lophurae
2.4.2.1 PNP
-
 Cellulomonas sp.
2.4.2.1 PNP
-
 Bos taurus
2.4.2.1 PNP
-
 Escherichia coli
2.4.2.1 PNP
-
 Plasmodium falciparum
2.4.2.1 PNP
-
 Homo sapiens
2.4.2.1 PNP
-
 Helicobacter pylori
2.4.2.1 PNP-II
-
 Escherichia coli
2.4.2.1 punA
-
 Cellulomonas sp.
2.4.2.1 xanthosine phosphorylase
-
 Escherichia coli
2.4.2.1 XAP
-
 Escherichia coli
2.4.2.1 xapA
-
 Escherichia coli

Ki Value [mM]

EC Number Ki Value [mM] Ki Value maximum [mM] Inhibitor Comment Organism Structure
2.4.2.1 0.000000005
-
 SerMe-immucillin-H pH and temperature not specified in the publication Homo sapiens
2.4.2.1 0.000000009
-
 DADMe-immucillin-H pH and temperature not specified in the publication Homo sapiens
2.4.2.1 0.000000009
-
 DATMe-immucillin-H pH and temperature not specified in the publication Homo sapiens
2.4.2.1 0.000000023
-
 DADMe-immucillin-H pH and temperature not specified in the publication Bos taurus
2.4.2.1 0.000000058
-
 immucillin-H pH and temperature not specified in the publication Homo sapiens
2.4.2.1 0.0000044
-
 DFPP-DG pH and temperature not specified in the publication Bos taurus
2.4.2.1 0.0000135
-
 9-(3-pyridylmethyl)-9-deaza-guanosine pH and temperature not specified in the publication Homo sapiens
2.4.2.1 0.0003
-
 6-methylformycin A pH and temperature not specified in the publication Escherichia coli
2.4.2.1 0.005
-
 formycin B pH and temperature not specified in the publication Escherichia coli
2.4.2.1 0.1
-
 formycin B pH and temperature not specified in the publication Homo sapiens

Expression

EC Number Organism Comment Expression
2.4.2.1 Escherichia coli Escherichia coli PNP-II (xanthosine phosphorylase) is inducible by xanthosine up

General Information

EC Number General Information Comment Organism
2.4.2.1 evolution in some organisms, like Escherichia coli, two distinct forms of PNP exist, with markedly different structure and substrate specificity. The second form, the so-called E. coli PNP-II, is sometimes referred to as xanthosine phosphorylase, since it is inducible by this nucleoside, but its specificity is not limited to this compound, and includes guanosine, inosine and nicotinamide riboside Escherichia coli
2.4.2.1 evolution in some organisms, like Escherichia coli, two distinct forms of PNP exist, with markedly different structure and substrate specificity. The second form, the so-called Escherichia coli PNP-II, is sometimes referred to as xanthosine phosphorylase, since it is inducible by this nucleoside, but its specificity is not limited to this compound, and includes guanosine, inosine and nicotinamide riboside Escherichia coli
2.4.2.1 evolution the homodimeric PNP from Ervinia carotovora cannot be assigned to the two described PNP classes, trimeric and hexameric PNPs Pectobacterium carotovorum
2.4.2.1 evolution the homotetrameric PNP from Baccilus cereus cannot be assigned to the two described PNP classes, trimeric and hexameric PNPs Bacillus cereus
2.4.2.1 evolution the pentameric PNP from Plasmodium lophurae cannot be assigned to the two described PNP classes, trimeric and hexameric PNPs Plasmodium lophurae
2.4.2.1 evolution the PNP from Cellulomonas sp. cannot be assigned to the any of two described PNP classes, trimeric and hexameric PNPs Cellulomonas sp.
2.4.2.1 evolution the PNP from Thermus thermophilus cannot be assigned to the any of two described PNP classes, trimeric and hexameric PNPs Thermus thermophilus
2.4.2.1 malfunction substrate specificity of trimeric and hexameric PNPs may be changed by mutations of the crucial active site amino acids, namely Asp in hexameric PNPs and Asn in trimeric PNPs Thermus thermophilus
2.4.2.1 malfunction substrate specificity of trimeric and hexameric PNPs may be changed by mutations of the crucial active site amino acids, namely Asp in hexameric PNPs and Asn in trimeric PNPs Cellulomonas sp.
2.4.2.1 malfunction substrate specificity of trimeric and hexameric PNPs may be changed by mutations of the crucial active site amino acids, namely Asp in hexameric PNPs and Asn in trimeric PNPs Bos taurus
2.4.2.1 malfunction substrate specificity of trimeric and hexameric PNPs may be changed by mutations of the crucial active site amino acids, namely Asp in hexameric PNPs and Asn in trimeric PNPs Escherichia coli
2.4.2.1 malfunction substrate specificity of trimeric and hexameric PNPs may be changed by mutations of the crucial active site amino acids, namely Asp in hexameric PNPs and Asn in trimeric PNPs Homo sapiens
2.4.2.1 physiological function Escherichia coli PNP converts pro-drugs, which are relative nontoxic purine nucleosides (for example 6-methyl purine 2'-deoxynucleoside or fludarabine), to their respective purine analogues (here, to 6-methylpurine and 2-fluoroadenine, respectively), which are very potent, toxic drugs Escherichia coli