Novel disintegrin-like peptides derived from an amphibian skin cDNA sequence of Hypsiboas punctatus.

Disintegrins comprise a family of small proteins that bind to and alter the physiological function of integrins, especially integrins that mediate platelet aggregation in blood. Here, we report a lysine-glycine-aspartic acid (KGD) disintegrin-like motif present in a 15-amino acid residue peptide identified in a cDNA library of the amphibian Hypsiboas punctatus skin. The original peptide sequence was used as a template from which five new analogs were designed, chemically synthesized by solid phase, and tested for disintegrin activity and tridimensional structural studies using NMR spectroscopy. The original amphibian peptide had no effect on integrin-mediated responses. Nevertheless, derived peptide analogs inhibited integrin-mediated platelet function, including platelet spreading on fibrinogen.

Isobenzofuran-1(3H)-ones as new tyrosinase inhibitors: Biological activity and interaction studies by molecular docking and NMR.

Tyrosinase is a multifunctional, glycosylated and copper-containing oxidase enzyme that can be found in animals, plants, and fungi. It is involved in several biological processes such as melanin biosynthesis. In this work, a series of isobenzofuran-1(3H)-ones was evaluated as tyrosinase inhibitors. It was found that compounds phthalaldehydic acid (1), 3-(2,6-dihydroxy-4-isopropylphenyl)isobenzofuran-1(3H)-one (7), and 2-(3-oxo-1,3-dihydroisobenzofuran-1-yl)-1,3-phenylene diacetate (9) were the most potent compounds inhibiting tyrosinase activity in a concentration dependent manner. Ligand-enzyme NMR studies and docking investigations allowed to map the atoms of the ligands involved in the interaction with the copper atoms present in the active site of the tyrosinase. This behaviour is similar to kojic acid, a well know tyrosinase inhibitor and used as positive control in the biological assays. The findings herein described pave the way for future rational design of new tyrosinase inhibitors.

A previously undescribed hexapeptide His-Arg-Phe-Leu-Arg-His-NH2 from amphibian skin secretion shows CO2 and metal biding affinities.

A previously undescribed six residues long peptide His-Arg-Phe-Leu-Arg-His was identified and purified from the skin secretion of the amphibian Phyllomedusa centralis. A synthetic analogue carboxyamidated HRFLRH-NH2 showed structural changes induced by CO2 and metal ions in aqueous solution when analyzed by NMR. The present work reports NMR structures for the carboxyamidated hexapeptide in the presence CO2, Zn2+ and Cd2+, suggesting possible affinity regions on the polypeptide chain for each ligand. The NMR structures were optimized by DFT to identify probable biding sites of these species in the polypeptide structure. To our best knowledge, this is the first time that a putative CO2 binding site is described on a peptide structure obtained in aqueous conditions, at room temperature.