Fluoro-olefins as peptidomimetic inhibitors of dipeptidyl peptidases.

The feasibility of the fluoro-olefin function as a peptidomimetic group in inhibitors for dipeptidyl peptidase IV and II (DPP IV and DPP II) is investigated by evaluation of N-substituted Gly-Psi[CF=C]pyrrolidines, Gly-Psi[CF=C]piperidines, and Gly-Psi[CF=C](2-cyano)pyrrolidines. Of this later class, the (Z)- and (E)-fluoro-olefin analogues were prepared and chemical stability in comparison with the parent amide was checked. Most of these compounds exhibited a strong binding preference toward DPP II with IC(50) values in the low micromolar range, while only low DPP IV inhibitory potential is seen.

Kinetic investigation of human dipeptidyl peptidase II (DPPII)-mediated hydrolysis of dipeptide derivatives and its identification as quiescent cell proline dipeptidase (QPP)/dipeptidyl peptidase 7 (DPP7).

The presence of DPPII (dipeptidyl peptidase II; E.C. 3.4.14.2) has been demonstrated in various mammalian tissues. However, a profound molecular and catalytic characterization, including substrate selectivity, kinetics and pH-dependence, has not been conducted. In the present study, DPPII was purified from human seminal plasma to apparent homogeneity with a high yield (40%) purification scheme, including an inhibitor-based affinity chromatographic step. The inhibitor lysyl-piperidide (K(i) approximately 0.9 microM at pH 5.5) was chosen, as it provided a favourable affinity/recovery ratio. The human enzyme appeared as a 120 kDa homodimer. Mass spectrometric analysis after tryptic digestion together with a kinetic comparison indicate strongly its identity with QPP (quiescent cell proline dipeptidase), also called dipeptidyl peptidase 7. pH profiles of both kcat and kcat/K(m) clearly demonstrated that DPPII/QPP possesses an acidic and not a neutral optimum as was reported for QPP. Kinetic parameters of the human natural DPPII for dipeptide-derived chromogenic [pNA (p-nitroanilide)] and fluorogenic [4Me2NA (4-methoxy-2-naphthylamide)] substrates were determined under different assay conditions. DPPII preferred the chromogenic pNA-derived substrates over the fluorogenic 4Me2NA-derived substrates. Natural human DPPII showed high efficiency towards synthetic substrates containing proline at the P1 position and lysine at P2. The importance of the P1' group for P2 and P1 selectivity was revealed, explaining many discrepancies in the literature. Furthermore, substrate preferences of human DPPII and dipeptidyl peptidase IV were compared based on their selectivity constants (kcat/K(m)). Lys-Pro-pNA (k(cat)/K(m) 4.1x10(6) s(-1) x M(-1)) and Ala-Pro-pNA (kcat/K(m) 2.6x10(6) s(-1) x M(-1)) were found to be the most sensitive chromogenic substrates for human DPPII, but were less selective than Lys-Ala-pNA (kcat/K(m) 0.4x10(6) s(-1) x M(-1)).

Gamma-amino-substituted analogues of 1-[(S)-2,4-diaminobutanoyl]piperidine as highly potent and selective dipeptidyl peptidase II inhibitors.

Using 1-[(S)-2,4-diaminobutanoyl]piperidine as lead compound, we developed a large series of highly potent and selective dipeptidyl peptidase II (DPP II) inhibitors. gamma-Amino substitution with arylalkyl groups, for example, a 2-chlorobenzyl moiety, resulted in a DPP II inhibitor with an IC(50) = 0.23 nM and a high selectivity toward DPP IV (IC(50) = 345 microM). Furthermore, it was shown that the basicity of the gamma-amino is important and that alpha-amino substitution is not favorable. Piperidine-2-nitriles did not show an increase in potency but rather reduced the selectivity. Introduction of a 4-methyl or a 3-fluorine on piperidine improved selectivity and preserved the high potency.

Design, synthesis, and SAR of potent and selective dipeptide-derived inhibitors for dipeptidyl peptidases.

In this paper we report the systematic search for new, potent, and selective DPP II inhibitors. A study of the structure-activity relationship was conducted starting from aminoacyl pyrrolidides as lead compounds. Rational exploration of the P(1) and P(2) building blocks led to the discovery of some very potent DPP II inhibitors which can be characterized by their high selectivity for DPP II with regard to DPP IV. Dab-Pip and Dab-Pip-2-CN were selected as the most promising inhibitors (IC(50) nM range) and will enable us to study the physiological role of DPP II and to differentiate between DPP II and DPP IV in biological systems.

Rapid parallel synthesis of dipeptide diphenyl phosphonate esters as inhibitors of dipeptidyl peptidases.

In this paper, we present a parallel synthesis of several series of dipeptide diphenyl phosphonates that are known to be irreversible inhibitors of serine proteases. Polymer-assisted solution-phase synthesis (PASP) is used for the rapid and clean coupling between various alpha-aminoalkyl diphenyl phosphonate ester building blocks and commercially available or easily accessible amino acids. These compounds were used for the rapid profiling of dipeptidyl peptidase II (DPP II) and the closely related dipeptidyl peptidase IV (DPP IV). A highly selective DPP II inhibitor was identified, N-cyclopentylglycyl-NHCH(C(6)H(5))PO(OPh)(2) (9.35), that will be useful to discriminate between DPP II and DPP IV in biological systems in order to further elucidate the biological function of DPP II.

Development of potent and selective dipeptidyl peptidase II inhibitors.

Structure-activity investigations of product-like dipeptide analogues lacking the C-terminal carbonyl function resulted in potent and selective dipeptidyl peptidase II (DPP II) inhibitors. Dab-Pip has an IC(50)=0.13 microM for DPP II and a 7600-fold selectivity with respect to DPP IV. This compound will be highly valuable for the investigation of the biochemical function of DPP II.