Synthesis and structure of prolinal-containing peptides, and their use as specific inhibitors of prolyl endopeptidases

New highly potent GABA uptake inhibitors selective for GAT-1 and GAT-3 derived from (R)- and (S)-proline and homologous pyrrolidine-2-alkanoic acids

We synthesized proline and pyrrolidine-2-alkanoic acid derivatives in their enantiomerically pure form and evaluated them for their affinity to the GABA transport proteins GAT-1 and GAT-3. Among the compounds presented herein, (R)-pyrrolidine-2-acetic acid (R)-4d substituted with a 2-[tris(4-methoxyphenyl)methoxy]ethyl residue at the nitrogen atom showed the highest affinity at GAT-3 (IC(50) = 3.1 microM) comparable with the well-known GAT-3 blocker (S)-SNAP-5114. Compound (R)-4d displayed excellent subtype selectivity for GAT-3 (GAT-3:GAT-1 = 20:1). (S)-2-pyrrolidineacetic acid derivatives (S)-4b provided with a 4,4-diphenylbut-3-en-1-yl moiety and (S)-4c substituted with a 4,4-[di(3-methylthiophen-2-yl)]phenylbut-3-en-1-yl residue at the nitrogen atom exhibited IC(50) values of 0.396 microM and 0.343 microM at the GAT-1 protein, respectively.

Salivary histatin as an inhibitor of a protease produced by the oral bacterium Bacteroides gingivalis

We examined the effect of histatin 5 from human parotid saliva on various proteases. Histatin 5 strongly inhibited a trypsin-like protease produced by Bacteroides gingivalis with an IC50 value of 55 nM. Clostripain was also inhibited (IC50 = 800 nM). Activities of other proteases were not affected significantly. Because B. gingivalis is a suspected periodontal pathogen and its proteolytic enzymes have been considered to be associated with periodontal tissue destruction, it is suggested that salivary histatins play a role as a preventive against periodontal disease.

Synthesis and inhibitory activity of acyl-peptidyl-pyrrolidine derivatives toward post-proline cleaving enzyme; a study of subsite specificity

Several pyrrolidine derivatives have been synthesized and examined for their inhibitory activity on post-proline cleaving enzymes from Flavobacterium meningosepticum and bovine brain. Almost all the compounds tested in this study inhibited the activity of both enzymes at low IC50 values (from nM to microM) but a specificity difference was observed with alkylacyl-peptidyl-pyrrolidine derivatives which strongly inhibited only the bacterial enzyme. The most effective inhibitors have a proline residue on their P2 sites and a substituted or unsubstituted phenoxybutyryl moiety on their P3 sites. Thus phenoxybutyryl-prolyl-pyrrolidine is the most effective partial structure of the inhibitors. The best inhibitors found were: 4-(4-benzylphenoxy)butyryl-prolyl-pyrrolidine for bacterial enzyme (IC50 1.4 nM) and 4-phenylbutyryl-thioprolyl-pyrrolidine for bovine brain enzyme (IC50 67 nM). In the passive avoidance test, using amnesic rats experimentally induced with scopolamine, the pyrrolidine derivatives which had potent inhibitory activity toward post-proline cleaving enzymes also showed strong anti-amnesic activities at doses of 1-5 mg/kg, i.p.

Synthesis and inhibitory activity of acyl-peptidyl-prolinalderivatives toward post-proline cleaving enzyme as nootropic agents

Several prolinal derivatives were synthesized and examined for their inhibitory activity on post-proline cleaving enzymes from Flavobacterium meningosepticum and bovine brain and their possible properties as nootropic agents. Almost all the compounds tested inhibited the activity of both enzymes at low IC50 values of the order of nM, but a specificity difference was observed with alkylacyl-prolinal derivatives which strongly inhibited only the bacterial enzyme. Prolyl-prolinal derivatives were the most effective inhibitors for both enzymes. In the passive avoidance test using amnesic rats experimentally induced with scopolamine, the prolinal derivatives that have potent inhibitory activity toward post-proline cleaving enzymes showed also strong anti-amnesic activities at dose of 10-1000 micrograms/kg, i.p. Some of the compounds showed a bell-shape dose dependency. These results suggest that the post-proline cleaving enzymes play an important role in the regulation of learning and memory consolidation in the brain and inhibitors of these enzymes are suggested as possible candidates for nootropic agents, particularly for an anti-amnesic drug.

Involvement of prolyl endopeptidase in ascidian fertilization

Inhibitory effects on fertilization of the ascidian of three benzyloxycarbonyl(Z)-aminoacyl prolinals and Z-Gly-Pro-chloromethyl ketone added before and after insemination were examined. The results suggest that the prolyl endopeptidase is involved in the process of fertilization, especially in a process taking place between chorion elevation and cell cleavage.