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Literature summary extracted from

  • Page, J.P.; Munagala, N.R.; Wang, C.C.
    Point mutations in the guanine phosphoribosyltransferase from Giardia lamblia modulate pyrophosphate binding and enzyme catalysis (1999), Eur. J. Biochem., 259, 565-571.
    View publication on PubMed

Cloned(Commentary)

EC Number Cloned (Comment) Organism
2.4.2.8 functional overexpression of wild-type enzyme and expression of mutants in Escherichia coli Giardia intestinalis

Protein Variants

EC Number Protein Variants Comment Organism
2.4.2.8 A72G site-directed mutagenesis, exchange in diphosphate binding site, decreased Km-value for diphosphate and guanine, increased Km-value for 5-phosphoribosyl 1-diphosphate, reduced activity Giardia intestinalis
2.4.2.8 G71A site-directed mutagenesis, no activity Giardia intestinalis
2.4.2.8 G71E site-directed mutagenesis, no activity Giardia intestinalis
2.4.2.8 G71R site-directed mutagenesis, no activity Giardia intestinalis
2.4.2.8 T70K site-directed mutagenesis, exchange in diphosphate binding site, 6.7fold lower Km-value for diphosphate, lower Km for guanine, 2fold increase in Km-value for 5-phosphoribosyl 1-diphosphate, reduced activity Giardia intestinalis
2.4.2.8 T70K/A72G site-directed mutagenesis, exchange in diphosphate binding site, decreased Km-value for diphosphate and guanine, increased Km-value for 5-phosphoribosyl 1-diphosphate, reduced activity Giardia intestinalis

Inhibitors

EC Number Inhibitors Comment Organism Structure
2.4.2.8 5-phospho-alpha-D-ribose 1-diphosphate competitive against GMP; product inhibition Giardia intestinalis
2.4.2.8 GMP competitive against 5-phospho-alpha-D-ribose 1-diphosphate; product inhibition Giardia intestinalis

KM Value [mM]

EC Number KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
2.4.2.8 additional information
-
 additional information Km-values of mutant enzymes Giardia intestinalis
2.4.2.8 0.016
-
 guanine wild-type enzyme Giardia intestinalis
2.4.2.8 0.0225
-
 GMP wild-type enzyme, reverse reaction Giardia intestinalis
2.4.2.8 0.026
-
 5-phospho-alpha-D-ribose 1-diphosphate wild-type enzyme Giardia intestinalis
2.4.2.8 0.324
-
 diphosphate wild-type enzyme, reverse reaction Giardia intestinalis

Metals/Ions

EC Number Metals/Ions Comment Organism Structure
2.4.2.8 Mg2+
-
 Giardia intestinalis

Organism

EC Number Organism UniProt Comment Textmining
2.4.2.8 Giardia intestinalis
-
-
-

Purification (Commentary)

EC Number Purification (Comment) Organism
2.4.2.8 recombinant wild-type enzyme and mutants from Escherichia coli Giardia intestinalis

Reaction

EC Number Reaction Comment Organism Reaction ID
2.4.2.8 IMP + diphosphate = hypoxanthine + 5-phospho-alpha-D-ribose 1-diphosphate ordered bi-bi mechanism Giardia intestinalis
a

Substrates and Products (Substrate)

EC Number Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
2.4.2.8 guanine + 5-phospho-alpha-D-ribose 1-diphosphate absolutely specific for guanine Giardia intestinalis GMP + diphosphate diphosphate binds at Thr70, diphosphate-binding loop sequence: LTGA r
2.4.2.8 hypoxanthine + 5-phospho-alpha-D-ribose 1-diphosphate no activity with hypoxanthine Giardia intestinalis IMP + diphosphate
-
 ?
2.4.2.8 xanthine + 5-phospho-alpha-D-ribose 1-diphosphate no activity Giardia intestinalis XMP + diphosphate
-
 ?

Temperature Optimum [°C]

EC Number Temperature Optimum [°C] Temperature Optimum Maximum [°C] Comment Organism
2.4.2.8 37
-
 assay at Giardia intestinalis

Turnover Number [1/s]

EC Number Turnover Number Minimum [1/s] Turnover Number Maximum [1/s] Substrate Comment Organism Structure
2.4.2.8 additional information
-
 additional information kcat of mutant enzymes Giardia intestinalis
2.4.2.8 5.7
-
 guanine wild-type enzyme Giardia intestinalis
2.4.2.8 5.8
-
 GMP wild-type enzyme, reverse reaction Giardia intestinalis
2.4.2.8 74.8
-
 5-phospho-alpha-D-ribose 1-diphosphate wild-type enzyme, forward reaction Giardia intestinalis
2.4.2.8 76.7
-
 guanine wild-type, forward reaction Giardia intestinalis

pH Optimum

EC Number pH Optimum Minimum pH Optimum Maximum Comment Organism
2.4.2.8 7.5
-
 assay at Giardia intestinalis

Ki Value [mM]

EC Number Ki Value [mM] Ki Value maximum [mM] Inhibitor Comment Organism Structure
2.4.2.8 additional information
-
 additional information kinetics for product inhibition in forward and reverse reaction, wild-type enzyme Giardia intestinalis