Synthesis, Molecular Simulation Of Cyclic Tetrapeptide Histone Deacetylases Inhibitors

HDACs that regulate some genes expression of the cells and the activity of regulatory factor, and over expression of HDACs correlate very closely with tumorigenesis. HDACIs could induce growth arrest, differentiation and apoptosis of tumor cells, so HDACIs represent one of the most promising epigenetic treatments for cancer. Currently,18HDACs have been identified in humans, and they are subdivided into four classes based on their homology to yeast HDACs. Class I (HDAC1-3,8) and class Ⅱ (HDAC4-7,9,10) require Zn2+for their activity to regulate gene expression, and are focused on the research of drug target. Via X-ray to obtain crystal structure analysis of HDLP, HDAC2, HDAC4, HDAH, HDAC7and HDAC8. Basic on the structure of HDACIs indicate that the metal binding site to determine the inhibitory activity of the inhibitor, and the surface recognition has an important effect on inhibitor activity and selectivity. In this paper, we used computer aided drug design and liquid phase peptide synthesis method to study on the effects of metal binding site and surface recognition on inhibitor activity and selectivity of HDACIs of the cyclic peptide, and synthesis better activity and selectivity of HDACIs.(1) We used molecular docking and dynamics simulations to analysis metal binding site and surface recognition of HDACIs of the cyclic peptide. The results show that HDACIs have the best inhibitory activity containing hydroxamic acid groups; the hydrophobicity of amino acids at2-position in the surface recognition only influence the activity of inhibitor, but not its selectivity; amino acids at3-position in the surface recognition has important effect on selectivity of HDACIs.(2) To obtain potent and selective HDACIs, we basiced on the above analysis results, used HC-toxin as lead compound and based on the structure of cyclo(-L-Asu (NHOH)-Aib-L-Phe-D-Pro-), and replaced L-Phe to L,-Ac5(or L-Ac6) in order to examine whether the hydrophobicity and the length of the side chain of amino acids at3-position in the surface recognition had effect on the activity and selectivity of HDACIs. In this paper we synthesized two cyclic tetrapeptide HDACIs:cyclo(-L-Asu (NHOH)-Aib-L-Ac5-D-Pro-)(HDACI15) and cyclo(-L-Asu(NHOH)-Aib-L-Ac6-D-Pro-)(HDACI16). HPLC and mass spectrometry detection results showed consistency with the target compounds, the purity was98%. CD results shown that HDACIs1,15-16have similar conformations. The activity results of new synthesis inhibitors showed that inhibitors had potent suppression activity and IC50values€in the nanomolar range. Tow compounds both showed better activity against HDAC1and HDAC4than HDAC6and their selectivity was better (HDACI15: HDAC6/HDAC1=7.9, HDACI16:HDAC6/HDACI=12.2). When the length of the side chain of amino acids contained four CH2groups, inhibitor had the better activity and selectivity (it is HDACI16).Combined with suppression activity and molecular docking results of inhibitors showed that amino acids has important effect on selectivity and activity of inhibitors at3-position in the surface recognition, and the reason that inhibitors were poorly inhibited by HDAC6may be a narrow of enzyme pocket mouth of HDAH, moreover, amino acids were weaker hydrophobicity than HDAC2and HDAC4at the enzyme activity pocket edge.