Peptidyl beta-homo-aspartals (3-amino-4-carboxybutyraldehydes): new specific inhibitors of caspases.
Interleukin-1 beta (IL-1 beta)-converting enzyme (ICE, caspase-1) processes the IL-1 beta precursor to mature inflammatory cytokine IL-1 beta. ICE has been identified as a unique cysteine protease, which cleaves Asp-X bonds, shows resistance to E-64 (an inhibitor of most cysteine proteases) and has a primary structure that is homologous to CED-3, a protein required for apoptosis (programmed cell death) in the nematode Caenorhabditis elegans, and to mammalian cysteine proteases that initiate and execute apoptosis, e.g., apopain/CPP32/caspase-3. The inhibitors of the ICE/CED-3 family or caspases, as they are called recently, may constitute therapeutic agents for amelioration of inflammatory and apoptosis-associated diseases. The most efficient ICE inhibitors are peptide aldehydes and peptidyl chloro or (acyloxy)methanes. A recent study revealed that both D- and L-Asp are accepted by ICE at the P1 of such inhibitors, and the peptidyl (acyloxy)methane analogues having the beta-homo-aspartyl residue [-NH-CH(CH2COOH)-CH2CO-] are inactive. These findings we reexamined in terms of two issues. (a) ICE's resistance to E-64. Since it was thought to be caused by the enzyme's unique substrate specificity, we prepared substrate-based analogues, which were not inhibitory suggesting significant structural difference between the active centers of ICE and papain-like enzymes. (b) Tolerance for D-stereochemistry at the P1 of these inhibitors. In view of the mechanism of cysteine protease inhibition by peptidyl X-methanes, we thought that this phenomenon should be a general characteristic of cysteine proteases and the hAsp-containing analogues should behave as reversible inhibitors. Here, we analyzed the inhibition of ICE and apopain in comparison with that of papain, thrombin, and trypsin by peptide L/D-alpha-aldehydes and their L-beta-homo-aldehyde [-NH-CH(R)-CH2-CHO] analogues. The following results were found. (1) The peptidyl L-beta-homo-aspartals are potent inhibitors for caspases. (2) The L-beta-homo analogues of peptide aldehyde inhibitors designed for other proteases are not inhibitory. (3) Unlike trypsin and thrombin (serine proteases), papain (cysteine protease) shows tolerance for D-stereochemistry at the P1 site of peptide aldehydes in proportion to the lability of the alpha-hydrogen of the P1-D-residue. The complete tolerance of ICE for P1-D-Asp may arise from this residue's high tendency to epimerization. (4) Reaction of cysteine proteases with peptide aldehyde or peptidyl X-methane inhibitors containing P1-D-residues may include alpha-proton abstraction followed by asymmetric induction leading to P1-L-residue-containing products.
Bajusz
S
S
Institute for Drug Research, Budapest, Hungary.
Fauszt
I
I
Németh
K
K
Barabás
E
E
Juhász
A
A
Patthy
M
M
Bauer
P I
PI
D000447:Aldehydes; D001665:Binding Sites; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D010206:Papain / Q000037:antagonists & inhibitors; D015842:Serine Proteinase Inhibitors / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D013329:Structure-Activity Relationship; D013917:Thrombin / Q000037:antagonists & inhibitors; D014361:Trypsin Inhibitors / Q000737:chemistry
D000447:Aldehydes; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D009842:Oligopeptides; D015842:Serine Proteinase Inhibitors; D014361:Trypsin Inhibitors; D013917:Thrombin; D010206:Papain; C018475:butyraldehyde