nitrophenols and bromoacetate

The kinetics of inhibition of penaeus penicillatus acid phosphatase by bromoacetic acid has been studied. The results show that inhibition of the enzyme by bromoacetic acid is a slow, reversible reaction. The microscopic rate constants for the reaction of inhibitor with the enzyme were determined. The presence of the substrate offers marked protection of this enzyme against inhibition by bromoacetic acid. The above results suggest that the histidine residue is essential for activity and are situated at the active site of the enzyme.

Topics: Acetates; Acid Phosphatase; Animals; Dose-Response Relationship, Drug; Enzyme Inhibitors; Kinetics; Nitrophenols; Organophosphorus Compounds; Penaeidae

Cyanogen (C2N2), a molecule with properties remarkably similar to carbon dioxide, differentially inhibits three of the four carbonic anhydrases reported here. Bovine carbonic anhydrase II shows 97% loss of esterase activity with no concommitant loss in hydratase activity. The hydratase and esterase activities of human carbonic anhydrase I are decreased by 80% and 55% respectively. Canine carbonic anhydrase shows similar results to human carbonic anhydrase I, retaining 29% hydratase and 62% esterase activity. Rabbit carbonic anhydrase sustained no loss of either hydratase or esterase activity. This inhibition occurs by an irreversible modification of the enzymes. The kinetic parameters for modified and unmodified enzymes were altered in a way that reflects the characteristic effect for each carbonic anhydrase.

Topics: Acetates; Acetazolamide; Animals; Carbon Dioxide; Carbonic Anhydrase Inhibitors; Cattle; Dogs; Humans; Iodoacetamide; Iodoacetates; Iodoacetic Acid; Kinetics; Nitriles; Nitrophenols; Pyruvates; Rabbits