Structural studies by 1H NMR and molecular modeling of peptide substrates of thermolysin in relation with its proteasic activity in water and glycerol.

In an attempt to explain the relationship between conformations of peptide substrates of thermolysin in natural form and the experimental enzymatic cleavages, five peptides of various length were studied in two solvents H2O and glycerol, which may mimic the catalytic environmental conditions. As NMR failed to define sufficiently rough constraints to ensure a convergence of a refinement process for such short and flexible peptides, the conformational space was first searched using the MCMM method. The generated structures were then clustered in families using a 0.

Additional data about thermolysin specificity in buffer- and glycerol-containing media.

Synthesis and use of various substrates permit an improved approach to thermolysin-peptide recognition and elucidation of several new criteria affecting enzyme specificity. Nature and position of the recognized residue, role of adjacent amino acids, lateral chain hydrophobicity, and volume and length of peptides were all considered. Hydrolysis reactions were also carried out in the presence of glycerol; the effect of microenvironment modifications was quantitative, for example in inducing variations in catalytic reaction rates, and also qualitative, such as in influencing affinity.

Investigation of the structural parameters involved in the delta-opioid selectivity of several families of opioid peptides.

Three series of highly delta-opioid selective peptides are now available, and each family is used as template to investigate the structural parameters involved in delta-receptor recognition and in the modulation of the selectivity of the parent peptide. The first series includes cyclic derivatives such as Tyr-D-Pen-Gly-Phe-D-Pen(DPDPE) and Tyr-D-Pen-Gly-Phe-Pen(DPLPE); the second are the synthetic linear constrained peptides [Tyr-D-Ser(OtBu)-Gly-Phe-Leu-Thr(DSTBULET), Tyr-D-Ser(OtBu)-Gly-Phe-Leu-Thr (OtBu)(BUBU) and especially Tyr-D-Cys(StBu)-Gly-Phe-Leu-Thr(OtBu) (BUBUC)] and the last one the natural peptides [Tyr-D-Met-Phe-His-Leu-Met-Asp-NH2 (deltorphin or dermenkephalin) and Tyr-D-Ala-Phe-Asp-Val-Val-GlyNH2 ([D-Ala2] deltorphin I)]. In the present study, the possibly of transposing some of the decisive factors of delta-selectivity evidenced in the two other families, to the linear constrained peptides series was examined.

The highly selective delta agonist BUBU induces an analgesic effect in normal and arthritic rat and this action is not affected by repeated administration of low doses of morphine.

The effect of various doses of the selective delta agonist BUBU (Tyr-D-Ser(O-t-butyl)-Gly-Phe-Leu-Thr(O-t-butyl) on the vocalization threshold to paw pressure were compared in normal and arthritic rats, a suitable clinical model of chronic pain. In both group of rats, the intravenous administration of BUBU (6, 9, 12 mg/kg in normal and 1.5, 3, 6 mg/kg in arthritic rats) led to significant antinociceptive effects.

Supraspinal mu 2-opioid receptors mediate spinal/supraspinal morphine synergy.

TRIMU-5 (Tyr-D-Ala-Gly-NHC2H4CH(CH3)2) is a potent mu 2-opioid agonist/mu 1-opioid antagonist. A supraspinal dose (0.5 micrograms i.