Synthetic peptide-based activators of the proteasome.
The development of small molecule peptide-based activators of the 20S proteasome or multicatalytic proteinase complex was initiated. The enhancement of antigen presentation by transfection of the protein activator PA28alpha into a mouse fibroblast cell line [10] supports the potential use of small molecule activators in stimulating the immune response. Four classes of peptide-based activators were synthesized, i.e. peptidyl alcohols, esters, p-nitroanilides and nitriles. These compounds markedly and reversibly stimulated the hydrolysis of suc-LLVY-MCA, Z-LLE-NA and Z-GPALG-p-aminobenzoate as well as hydrolysis of the decapeptide angiotensin I. Stimulation was due to a decrease in the Km and increase in the Vmax of the substrate. In general, the EC50 for activation ranged from 50-150 mM and maximal stimulation varied from 3 to 15 fold depending on the activity measured. Z-IE(Ot-Bu)AL-p-nitroanilide, a proteasome substrate, markedly stimulated the hydrolysis of Z-GPALG-pAB by binding to a saturable high affinity site distinct from its binding site as substrate. Since all effective activators contain hydrophobic groups in positions P1-P5, low aqueous solubility is a limitation of these compounds. Competition experiments suggest that these activators bind to the same site as PA28.
Wilk
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Department of Pharmacology, Mount Sinai School of Medicine, New York, NY 10029, USA.
Chen
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D000803:Angiotensin I / Q000378:metabolism; D000818:Animals; D002417:Cattle; D003374:Coumarins; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004789:Enzyme Activation; D006868:Hydrolysis; D007700:Kinetics; D009097:Multienzyme Complexes / Q000378:metabolism*; D009842:Oligopeptides / Q000138:chemical synthesis / Q000494:pharmacology*; D046988:Proteasome Endopeptidase Complex; D011506:Proteins / Q000494:pharmacology; D013329:Structure-Activity Relationship
D003374:Coumarins; D009097:Multienzyme Complexes; D009842:Oligopeptides; D011506:Proteins; D000803:Angiotensin I; C046582:succinyl-leucyl-leucyl-valyl-tyrosyl-methylcoumarinamide; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex