RESUMO
The presented research concerns the triple activity of trans-cinnamic (tCA), ferulic (FA) and syringic acids (SA). They act as thyroid peroxidase (TPO) activators, lipoxygenase (LOX) inhibitors and show antiradical activity. All compounds showed a dose-dependent TPO activatory effect, thus the AC50 value (the concentration resulting in 50% activation) was determined. The tested compounds can be ranked as follows: tCA > FA > SA with AC50 = 0.10, 0.39, 0.69 mM, respectively. Strong synergism was found between FA and SA. The activatory effects of all tested compounds may result from interaction with the TPO allosteric site. It was proposed that conformational change resulting from activator binding to TPO allosteric pocket results from the flexibility of a nearby loop formed by residues Val352-Tyr363. All compounds act as uncompetitive LOX inhibitors. The most effective were tCA and SA, whereas the weakest was FA (IC50 = 0.009 mM and IC50 0.027 mM, respectively). In all cases, an interaction between the inhibitors carboxylic groups and side-chain atoms of Arg102 and Arg139 in an allosteric pocket of LOX was suggested. FA/tCA and FA/SA acted synergistically, whereas tCA/SA demonstrated antagonism. The highest antiradical activity was found in the case of SA (IC50 = 0.22 mM). FA/tCA and tCA/SA acted synergistically, whereas antagonism was found for the SA/FA mixture.
Assuntos
Autoantígenos/metabolismo , Ativadores de Enzimas/farmacologia , Iodeto Peroxidase/metabolismo , Proteínas de Ligação ao Ferro/metabolismo , Inibidores de Lipoxigenase/farmacologia , Compostos Fitoquímicos/farmacologia , Proteína-Lisina 6-Oxidase/metabolismo , Autoantígenos/química , Cinamatos/química , Cinamatos/farmacologia , Ácidos Cumáricos/química , Ácidos Cumáricos/farmacologia , Relação Dose-Resposta a Droga , Ativadores de Enzimas/química , Ácido Gálico/análogos & derivados , Ácido Gálico/química , Ácido Gálico/farmacologia , Humanos , Concentração Inibidora 50 , Iodeto Peroxidase/química , Proteínas de Ligação ao Ferro/química , Inibidores de Lipoxigenase/química , Modelos Moleculares , Compostos Fitoquímicos/química , Proteína-Lisina 6-Oxidase/química , Relação Estrutura-AtividadeRESUMO
The sirtuin family comprises seven NAD+-dependent histone deacetylases named SIRT1 to SIRT7. The least investigated SIRT7 is currently considered as a promising therapeutic target for cardiovascular diseases, diabetes and different types of cancer. So far, its structure was not experimentally resolved, except of a fragment of its N-terminus. The aim of this study was to create in silico model of SIRT7 containing its core together with N-terminus, which is known to affect the enzyme's catalytic activity and to find pockets that could be targeted by structure-based virtual screening. Homology model of SIRT7 was prepared using X-ray structures of other sirtuins and a resolved fragment of the N-terminus of SIRT7 as templates. All atom-unbiased molecular dynamics simulations were performed. It was found that N-terminus of SIRT7 remains in spatial proximity of the catalytic core for considerable fraction of time, and therefore, it may affect its catalytic activity by helping the enzyme to hold the substrate peptide. It may also participate in holding and release of the cofactor. Preferred orientations of NAD+ and acetyl-lysine inside SIRT7 were found, with all components forming a stable complex. Molecular dynamics provided an ensemble of conformations that will be targeted with virtual screening. Reliable in silico structure of SIRT7 will be a useful tool in searching for its inhibitors, which can be potential drugs in cancer treatment.Communicated by Ramaswamy H. Sarma.