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Literature summary for 2.4.2.1 extracted from

  • Isaksen, G.V.; Aqvist, J.; Brandsdal, B.O.
    Thermodynamics of the purine nucleoside phosphorylase reaction revealed by computer simulations (2017), Biochemistry, 56, 306-312 .
    View publication on PubMed
Search for more literature for 2.4.2.1

Protein Variants

Protein Variants Comment Organism
K22E/H104R site-directed mutagenesis, mutation on the enzyme protein surface, the mutation alters the enthalpy-entropy balance with little effect on the catalytic rates Homo sapiens

KM Value [mM]

KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
additional information
-
 additional information analysis of the thermodynamic activation parameters for the glycosidic bond cleavage step in native HsPNP using the previously reported reaction mechanism. The higher activation enthalpy for ADO compared to those of INO and GUO further predicts that the reaction rate with ADO is significantly more temperature sensitive than those of the 6-oxopurines Homo sapiens

Natural Substrates/ Products (Substrates)

Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
adenosine + phosphate Homo sapiens very low activity adenine + alpha-D-ribose 1-phosphate
-
 r
guanosine + phosphate Homo sapiens
-
 guanine + alpha-D-ribose 1-phosphate
-
 r
inosine + phosphate Homo sapiens
-
 hypoxanthine + alpha-D-ribose 1-phosphate
-
 r

Organism

Organism UniProt Comment Textmining
Homo sapiens P00491
-
-

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
adenosine + phosphate very low activity Homo sapiens adenine + alpha-D-ribose 1-phosphate
-
 r
guanosine + phosphate
-
 Homo sapiens guanine + alpha-D-ribose 1-phosphate
-
 r
inosine + phosphate
-
 Homo sapiens hypoxanthine + alpha-D-ribose 1-phosphate
-
 r

Synonyms

Synonyms Comment Organism
HsPNP
-
 Homo sapiens
Ino-Guo phosphorylase
-
 Homo sapiens
PNP
-
 Homo sapiens
purine nucleoside phosphorylase
-
 Homo sapiens

Temperature Range [°C]

Temperature Minimum [°C] Temperature Maximum [°C] Comment Organism
additional information
-
 low activity toward 6-aminopurines at room temperature. Elevated temperatures act beneficially on the reaction rates by reducing the unfavorable contribution from the enthalpy of activation. The transition state with adenosine is less stabilized than those of inosine and guanosine. This largely originates from unfavorable interactions between the base and E201, which is repelled from the original N1 position observed for the 6-oxopurines. Molecular simulations, overview Homo sapiens

General Information

General Information Comment Organism
malfunction effect of remote mutations on the thermodynamic activation parameters of human purine nucleoside phosphorylase, overview. More than 2700 independent reaction free energy profiles for six different temperatures are calculated to obtain high-precision computational Arrhenius plots. On the basis of these, the activation enthalpies and entropies are computed from linear regression of the plots with DELTAG++ as a function of 1/T to obtain thermodynamic activation parameters. The substrate specificity is related to the difference in thermodynamic activation parameters. Remote mutations affect the activation enthalpy-entropy balance Homo sapiens
additional information the substrate specificity is related to the difference in thermodynamic activation parameters. Furthermore, the calculations show that the human PNP specificity for 6-oxopurines over 6-aminopurines originates from significant differences in electrostatic preorganization. Residues Y88, F200, E201, N243, and H257 interact with the nucleoside while S33, H64, R84, A116, S220, and two conserved waters interacting with the phosphate group are identified as key catalytic site residues. In addition, F159* from one adjacent subunit is oriented in the active site so that it makes contact with the nucleoside and shields it from the solvent Homo sapiens
physiological function purine nucleoside phosphorylase (PNP) catalyzes the reversible cleavage of the glycosidic bond of ribo- and 2'-deoxyribonucleosides, yielding the corresponding purine base and (2'-deoxy)ribose 1-phosphate as products. Enzyme HsPNP belongs to the low-molecular mass (low-mm) family of PNPs that generally are specific toward 6-oxopurines, e.g. inosine (INO) and guanosine (GUO), and thus are frequently termed Ino-Guo phosphorylases Homo sapiens