title: Purification and characterization of the hypoxanthine-guanine phosphoribosyltransferase from Saccharomyces cerevisiae.
abstract: 1. Hypoxanthine-guanine phosphoribosyltransferase (EC 2.4.2.8) from Saccharomyces cerevisiae was purified 9400-fold by affinity chromatography giving rise to an electrophoretically homogeneous preparation. 2. The molecular weight of the enzyme was determined by gel filtration with Sephadex G-100 and by sodium dodecylsulfate gel electrophoresis. Both methods reveal a molecular weight of 51,000. 3. The enzyme requires Mg2+ and has its pH optimum at 8.5. 4. Isoelectric focussing as well as gel electrophoresis of the purified extract reveals a single band which exhibits enzyme activity. The isoelectric point of the enzyme is 5.1. 5. The enzyme displays Michaelis-Menten kinetics with apparent Michaelis constants for hypoxanthine, guanine and phosphoribosylpyrophosphate of 23 microns, 18 microns, and 50 microns respectively.
mesh_terms: D007041:Hypoxanthine Phosphoribosyltransferase / Q000302:isolation & purification* / Q000378:metabolism; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008970:Molecular Weight; D012441:Saccharomyces cerevisiae / Q000201:enzymology*
chemical_list: D007041:Hypoxanthine Phosphoribosyltransferase; D008274:Magnesium