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PubMedDate not supplied

Inhibition of high voltage-activated Ca2+ currents from cultured sensory neurones by a novel insect peptide.

PMP-D2, a novel 35 amino acid peptide isolated from the brain of the locust Locusta migratoria, is localised specifically in neurosecretory cells and nerve tracts of the Pars intercerebralis. When PMP-D2 is applied onto rat sensory neurones it blocks high voltage-activated inward Ca2+ currents at concentrations ranging from 0.1 mu M to 10 mu M. The inhibitory effect of PMP-D2 is more marked on the sustained inward Ca2+ current measured at the end of 100 ms voltage step commands than on the maximum inward Ca2+ current. These results suggests that PMP-D2 may differentially inhibit the two components of the high voltage-activated inward Ca2+ currents of rat sensory neurones.

Animals↗
PubMedDate not supplied

Regioselective formation of the three disulfide bonds of a 35-residue insect peptide.

PMP-D2, a 35-residue peptide containing three disulfide bonds, was synthesized on solid-phase using 9-fluorenylmethoxy-carbonyl (Fmoc) as alpha-NH2 protection and simultaneous air oxidation of the six cysteines for formation of its disulfide bonds. The overall yield was 13%. As very little research has been done on the regioselective formation of three disulfide bonds, we decided to investigate different strategies using either trityl (Trt), acetamidomethyl (Acm) and methoxybenzyl (Mob), or methoxytrityl (Mmt), trityl and acetamidomethyl, as cysteine-protecting groups and Fmoc as alpha-NH2 protection. In the first strategy, the first disulfide bond was formed by air oxidation and the second was formed by iodine oxidation of the Cys(Acm). Then, the Cys (Mob) was deprotected using TFMSA/TFA treatment for formation of the third disulfide bond. This last step was poorly reproducible on a large scale. The overall yield was 2.5%. In the second strategy, the first disulfide was formed on the resin after removal of the methoxytrityl group, and the two remaining disulfide bonds were formed classically in solution. The overall yield was 2%. From the overall yields using these strategies, it appears clear that simultaneous oxidation of the six cysteines is particularly appropriate for the synthesis of PMP-D2.

Acetamides↗
PubMed1998

[New studies on natural inhibitors of proteolytic enzymes].

New data on proteolytic enzyme inhibitors and mechanisms of their interaction with the enzymes are reviewed. In recent years, a number of new inhibitors comprising families earlier unknown have been described such as proteins from the parasitic nematode Ascaris lumbricoides, ecotin from the periplasm of Escherichia coli, proteins PMP-C and PMP-D from locust Locusta migratoria, and hirustasin from the medicinal leech Hirudo medicinalis. At the same time, some proteins that may be assigned to inhibitors on the basis of their structures were found to perform other (not inhibitory) functions. Thus, the family of the Kunitz soybean trypsin inhibitor includes plant storage proteins and proteins whose synthesis is induced by stress factors. Numerous inhibitors interacting with the enzymes by mechanisms other than the substrate-like ones were identified, such as ornithodorin and anticoagulant peptide from tick Ornithodoros moubata (inhibitors of the blood clotting system proteases), an inhibitor from snake (Bothrops jararaca) venom, and ecotin, an inhibitor of serine proteases with an unusually broad specificity range. Special emphasis is placed on enzyme inhibition with propeptides and the mechanism of this process.

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