title: Chemical modification of the most reactive thiol group of rabbit skeletal muscle phosphofructokinase, to reduce its affinity toward substrate ATP and activating monovalent cations.
abstract: The most reactive single thiol group of rabbit skeletal muscle phosphofructokinase per protomer was modified with the following thiol reagents: iodoacetamide, iodoacetate, 2-hydroxyethyl disulfide, 3,3'-dithiodipropionate, and glutathione disulfide. As a result of the modification, there was increase in not only the apparent activation constants of activating monovalent cations, NH4+ (about 3-, 9-, 12-, 20-, and 30-fold, respectively) and K+ (about 3-, 10-, 15-, 17-, and 20-fold, respectively), but also the apparent Km for ATP (about 3-, 10-, 15-, 100-, and 20-fold, respectively) without any significant change in maximum velocity or apparent Km for fructose 6-phosphate in the presence of high concentrations of NH4+. These results suggest that modification of the thiol group destabilizes the enzyme-monovalent cation-MgATP complex proposed by Suelter [Science (1970) 168, 789-795], causing an apparent loss in catalytic activity.
authors.affiliation: Department of Biochemistry, Kitasato University School of Medicine, Kanagawa.
authors.forename: Y
authors.initials: Y
authors.lastname: Nakajima
authors.forename: K
authors.initials: K
authors.lastname: Nakamura
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000643:Ammonium Chloride / Q000378:metabolism*; D000818:Animals; D009132:Muscles / Q000201:enzymology*; D010732:Phosphofructokinase-1 / Q000378:metabolism*; D011189:Potassium Chloride / Q000378:metabolism*; D011817:Rabbits; D013379:Substrate Specificity; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D013438:Sulfhydryl Compounds; D000643:Ammonium Chloride; D011189:Potassium Chloride; D000255:Adenosine Triphosphate; D010732:Phosphofructokinase-1