nitrophenols and 4-bromophenacyl-bromide

Topics: Acetophenones; Amino Acid Sequence; Animals; Birds; Enzyme Stability; Epoxy Compounds; Hydrogen-Ion Concentration; Kinetics; Molecular Sequence Data; Nitrophenols; Norleucine; Pepsin A; Pepstatins; Protease Inhibitors; Thermodynamics

Two active site inhibitors of acid proteinases were tested for their effects on human neutrophil chemotaxis and lysosomal enzyme release. Both bromphenacyl bromide (BPAB) and epoxy-p-nitrophenoxypropane (EPNP) inhibited chemotaxis and chemotaxin-induced enzyme release elicited by pepstatin and formylmethionyl peptides, which share membrane receptors, and also by zymosan-activated serum, the major active component of which (C5a) occupies a different receptor. In contrast to the previously tested acid protease inhibitor diazoacetylnorleucine methyl ester, neither BPAB nor EPNP blocked binding of [3H]fMLP to neutrophils. Thus BPAB and EPNP inhibit chemotaxin-mediated neutrophil functions, but not by interaction with the chemotaxin receptor.

Topics: Acetophenones; Acid Phosphatase; Chemotaxis, Leukocyte; Dipeptides; Epoxy Compounds; Humans; Lysosomes; Muramidase; N-Formylmethionine; N-Formylmethionine Leucyl-Phenylalanine; Neutrophils; Nitrophenols; Oligopeptides; Pepstatins; Protease Inhibitors

1. The activity of chicken pepsin was partially inhibited by dimethyl-(2-hydroxy-5-nitrobenzyl)sulphonium bromide, but was unaffected by p-bromophenacyl bromide. 2. In the presence of Cu2+, diazoacetylnorleucine methyl ester completely inactivated chicken pepsin with the incorporation of 1 mol/mol. The mechanism of the reaction was similar to that with pig pepsin. 3. Chicken pepsin was completely inactivated by 2-diazo-4-bromoacetophenone in the presence of Cu2+. 4. Chicken pepsin was almost completely inactivated by 1,2-epoxy-3-(p-nitrophenoxy)propane at 25 degrees C, 3-4mol of inhibitor/mol being incorporated. The reaction at 10 degrees C was investigated briefly. 5. Calf chymosin was inactivated by 1,2-epoxy-3-(p-nitrophenoxy)propane at 10 degrees C, the incorporation of 1 mol/mol being required for complete inhibition. 6. The characteristics of the reactions of chicken pepsin with the above compounds were compared with those of other acid proteinases.

Topics: Acetophenones; Amino Acids; Azo Compounds; Chymosin; Copper; Hydrogen-Ion Concentration; Nitrophenols; Norleucine; Pepsin A; Proteins