Comparison of the effect of calpain inhibitors on two extralysosomal proteinases: the multicatalytic proteinase complex and m-calpain.
The potencies of three peptide aldehyde inhibitors of calpain (calpain inhibitors 1 and 2 and calpeptin) as inhibitors of four catalytic activities of the multicatalytic proteinase complex (MPC) were compared with their potencies as inhibitors of m-calpain. The chymotrypsinlike activity (cleavage after hydrophobic amino acids) and the caseinolytic activity (degradation of beta-casein) of MPC were strongly inhibited by calpain inhibitors 1 and 2 (IC50 values in the low micromolar range). Cleavage by MPC after acidic amino acids (peptidylglutamyl-peptide bond hydrolyzing activity) and basic amino acids (trypsinlike activity) was inhibited less effectively, declining moderately with increasing concentrations of calpain inhibitors 1 and 2. Calpeptin only weakly inhibited the four MPC activities, yet was the most potent inhibitor of m-calpain. These results indicate that caution must be exercised when calpain inhibitors 1 and 2 are used to infer calpain function. Calpeptin may be a better choice for such studies, although its effect on other cysteine or serine proteinases remains to be determined.
Figueiredo-Pereira
M E
ME
Department of Pharmacology, Mount Sinai School of Medicine, CUNY, New York 10029.
Banik
N
N
Wilk
S
S
D000595:Amino Acid Sequence; D000818:Animals; D002154:Calpain / Q000037:antagonists & inhibitors* / Q000302:isolation & purification / Q000378:metabolism*; D002417:Cattle; D003546:Cysteine Endopeptidases / Q000302:isolation & purification / Q000378:metabolism*; D004151:Dipeptides / Q000494:pharmacology*; D007700:Kinetics; D007976:Leupeptins / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000302:isolation & purification / Q000378:metabolism*; D009842:Oligopeptides / Q000378:metabolism / Q000494:pharmacology*; D010902:Pituitary Gland / Q000201:enzymology*; D011480:Protease Inhibitors / Q000494:pharmacology*; D046988:Proteasome Endopeptidase Complex; D013379:Substrate Specificity
D004151:Dipeptides; D007976:Leupeptins; D009097:Multienzyme Complexes; D009842:Oligopeptides; D011480:Protease Inhibitors; C063261:acetylleucyl-leucyl-norleucinal; C069861:calpain inhibitor 2; C071482:calpeptin; D002154:Calpain; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex