Catalytic Enantioselective Decarboxylative Protonation

We report a highly enantioselective, general catalytic system for the facile synthesis of tertiary stereocenters by protonation adjacent to cyclic ketones. The method relies on catalytic decarboxylative protonation of readily accessible racemic quaternary β-ketoesters. A range of substituted cycloalkanone compounds can be accessed through this process with high levels of enantioselectivity

Homogeneous Pd-Catalyzed Enantioselective Decarboxylative Protonation

General homogeneous conditions for the palladium-catalyzed synthesis of carbonyl compounds with tertiary carbon stereocenters at the α-position are reported. The highly reactive catalyst tolerates a variety of substrate substitution and functionality, and generates enantioenriched cyclic ketones from racemic allyl β-ketoester starting materials

Catalytic Enantioselective Decarboxylative Protonation

We report a highly enantioselective, general catalytic system for the facile synthesis of tertiary stereocenters by protonation adjacent to cyclic ketones. The method relies on catalytic decarboxylative protonation of readily accessible racemic quaternary β-ketoesters. A range of substituted cycloalkanone compounds can be accessed through this process with high levels of enantioselectivity

Identification of Dipeptidyl-Peptidase (DPP)5 and DPP7 in Porphyromonas endodontalis, Distinct from Those in Porphyromonas gingivalis

Dipeptidyl peptidases (DPPs) that liberate dipeptides from the N-terminal end of oligopeptides are crucial for the growth of Porphyromonas species, anaerobic asaccharolytic gram negative rods that utilize amino acids as energy sources. Porphyromonas endodontalis is a causative agent of periapical lesions with acute symptoms and Asp/Glu-specific DPP11 has been solely characterized in this organism. In this study, we identified and characterized two P. endodontalis DPPs, DPP5 and DPP7. Cell-associated DPP activity toward Lys-Ala-4-methylcoumaryl-7- amide (MCA) was prominent in P. endodontalis ATCC 35406 as compared with the Porphyromonas gingivalis strains ATCC 33277, 16-1, HW24D1, ATCC 49417, W83, W50, and HNA99. The level of hydrolysis of Leu-Asp-MCA by DPP11, Gly- Pro-MCA by DPP4, and Met-Leu-MCA was also higher than in the P. gingivalis strains. MER236725 and MER278904 are P. endodontalis proteins belong to the S9- and S46-family peptidases, respectively. Recombinant MER236725 exhibited enzymatic properties including substrate specificity, and salt- and pH-dependence similar to P. gingivalis DPP5 belonging to the S9 family. However, the kcat/Km figure (194 mM21?sec21) for the most potent substrate (Lys-Ala-MCA) was 18.4-fold higher as compared to the P. gingivalis entity (10.5 mM21?sec21). In addition, P. endodontalis DPP5 mRNA and protein contents were increased several fold as compared with those in P. gingivalis. Recombinant MER278904 preferentially hydrolyzed Met-Leu-MCA and exhibited a substrate specificity similar to P. gingivalis DPP7 belonging to the S46 family. In accord with the deduced molecular mass of 818 amino acids, a 105-kDa band was immunologically detected, indicating that P. endodontalis DPP7 is an exceptionally large molecule in the DPP7/DPP11/S46 peptidase family. The enhancement of four DPP activities was conclusively demonstrated in P. endodontalis, and remarkable Lys-Ala-MCAhydrolysis was achieved by qualitative and quantitative potentiation of the DPP5 molecule

Alignment of amino acid sequences of <i>P. endodontalis</i> MER278904 and <i>P. gingivalis</i> DPP7.

<p>The amino acid sequences of putative <i>P. endodontalis</i> DPP7 (PeDPP7, MER278904) and <i>P. gingivalis</i> DPP7 (PgDPP7, PGN_1479/MER014366) were aligned by Genetyx. Hyphens represent gaps introduced for maximal matching. Common amino acids are marked by asterisks. Three amino acids essential for serine proteases are written in red letters.</p

Biochemical analysis of putative PeDPP5 (MER236725).

<p>(A) Recombinant proteins (0.3 µg) of PgDPP5 (lane 1), putative PeDPP5 (lane 2), and aliquots (5 µL) of bacterial cell suspensions of <i>P. gingivalis</i> ATCC 33277 (lane 3), KDP136 (lane 4), and <i>P. endodontalis</i> (lanes 5 and 5C) were separated on SDS-PAGE gels, then stained with CB or subjected to immunoblotting (WB). The 100-kDa bands in lanes 5 and 5C were non-specifically observed with the alkaline phosphatase-conjugated second antibody. Lane M, molecular-weight markers. (B) NaCl-concentration dependence and (C) pH dependence of the hydrolyzing activity toward Lys-Ala-MCA of PgDPP5, putative PeDPP5 (MER236725), and <i>P. endodontalis</i> cells were determined. (D) The peptidase activities of recombinant PgDPP5 and PeDPP5 were determined using various dipeptidyl MCAs. Values are shown as the mean±S.D. (n = 3).</p