Inactivation of skeletal-muscle UDP-glucose pyrophosphorylase by reaction with carboxylate-directed reagents.
Skeletal-muscle UDP-glucose pyrophosphorylase is inactivated by reaction with 2-ethoxy-N-(ethoxy-carbonyl)-1,2-dihydroquinoline (EEDQ) and 1-(3-dimethylaminopropyl-3-ethylcarbodi-imide (EDAC), two reagents specific for carboxylate groups. The former reagent is a more effective inactivator than EDAC. Although no evidence of reversible enzyme-reagent complexes of the affinity-labelling type was obtained by kinetic analysis of the inactivation, the selective protection of UDP-glucose pyrophosphorylase activity against inactivation by EEDQ in the presence of uridine substrates is indicative of an active-site-directed effect. The results are consistent with the hypothesis that EEDQ modifies a single carboxylate group located in a hydrophobic domain close to the substrate-binding site, leading to enzyme inactivation. In contrast, the reaction between UDP-glucose pyrophosphorylase and EDAC appears to involve a different region of the enzyme.
Signorini
M
M
Istituto di Chimica Biologica, Universitá di Ferrara, Italy.
Ferrari
C
C
Mariotti
E
E
Dallocchio
F
F
Bergamini
C M
CM
D000818:Animals; D002234:Carbodiimides / Q000494:pharmacology*; D002264:Carboxylic Acids; D005022:Ethyldimethylaminopropyl Carbodiimide / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008024:Ligands; D008433:Mathematics; D008954:Models, Biological; D009132:Muscles / Q000201:enzymology*; D009713:Nucleotidyltransferases / Q000037:antagonists & inhibitors*; D011804:Quinolines / Q000494:pharmacology*; D011817:Rabbits; D005957:UTP-Glucose-1-Phosphate Uridylyltransferase / Q000037:antagonists & inhibitors*
D002234:Carbodiimides; D002264:Carboxylic Acids; D008024:Ligands; D011804:Quinolines; C000470:EEDQ; D009713:Nucleotidyltransferases; D005957:UTP-Glucose-1-Phosphate Uridylyltransferase; D005022:Ethyldimethylaminopropyl Carbodiimide