GONUTS has been updated to MW1.31 Most things seem to be working but be sure to report problems.

Have any questions? Please email us at ecoliwiki@gmail.com

PMID:7035445

From GONUTS
Jump to: navigation, search
Citation

Ali, LZ and Sloan, DL (1982) Studies of the kinetic mechanism of hypoxanthine-guanine phosphoribosyltransferase from yeast. J. Biol. Chem. 257:1149-55

Abstract

An assay procedure, utilizing high pressure liquid chromatography, has been designed which allows both reactions catalyzed by hypoxanthine-guanine phosphoribosyltransferase to be monitored simultaneously. Using this procedure and the theories described by Huang (Huang, C. V. (1979) Methods. Enzymol. 63, 486-500) for alternate substrate kinetic analysis, we have determined that purified hypoxanthine-guanine phosphoribosyltransferase from yeast catalyzes the formations of both IMP and GMP through the use of an Ordered Bi Bi kinetic mechanism, and that guanine is highly preferred over hypoxanthine as substrate in the forward reaction. This proposed kinetic mechanism has been confirmed using flow dialysis experiments in which a binary enzyme-5-phosphoribosyl-alpha-1-pyrophosphate complex was characterized but where enzymic complexes, with either guanine or hypoxanthine, were not detected. Also consistent with this kinetic mechanism was our observation that an exchange of label between [14C]guanine or [14C]hypoxanthine and their respective nucleotides (GMP and IMP) was not catalyzed by hypoxanthine-guanine phosphoribosyltransferase. However, a significant exchange of label between [32P]pyrophosphate and 5-phosphoribosyl-alpha-1-pyrophosphate is observed upon incubation with this enzyme, suggesting that hypoxanthine-guanine phosphoribosyltransferase may exist, in part, as a phosphoribosyl-enzyme complex in the presence of 5-phosphoribosyl-alpha-1-pyrophosphate.

Links

PubMed

Keywords

Carbon Radioisotopes; Chromatography, High Pressure Liquid; Hypoxanthine Phosphoribosyltransferase/isolation & purification; Hypoxanthine Phosphoribosyltransferase/metabolism; Kinetics; Mathematics; Saccharomyces cerevisiae/enzymology

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

YEAST:HPRT

enables

GO:0004422: hypoxanthine phosphoribosyltransferase activity

ECO:0000314: direct assay evidence used in manual assertion

F

Seeded From UniProt

complete

YEAST:HPRT

involved_in

GO:0032263: GMP salvage

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete

YEAST:HPRT

involved_in

GO:0032264: IMP salvage

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete

See also

References

See Help:References for how to manage references in GONUTS.