Dinucleosides with Non‐Natural Backbones: A New Class of Ribonuclease A and Angiogenin Inhibitors

Abstract

Ribonuclease A (RNase A) serves as a convenient model enzyme in the identification and development of inhibitors of proteins that are members of the ribonuclease superfamily. This is principally because the biological activity of these proteins, such as angiogenin, is linked to their catalytic ribonucleolytic activity. In an attempt to inhibit the biological activity of angiogenin, which involves new blood vessel formation, we employed different dinucleosides with varied non-natural backbones. These compounds were synthesized by coupling aminonucleosides with dicarboxylic acids and amino- and carboxynucleosides with an amino acid. These molecules show competitive inhibition with inhibition constant (K(i)) values of (59±3) and (155±5) μM for RNase A. The compounds were also found to inhibit angiogenin in a competitive fashion with corresponding K(i) values in the micromolar range. The presence of an additional polar group attached to the backbone of dinucleosides was found to be responsible for the tight binding with both proteins. The specificity of different ribonucleolytic subsites were found to be altered because of the incorporation of a non-natural backbone in between the two nucleosidic moieties. In spite of the replacement of the phosphate group by non-natural linkers, these molecules were found to selectively interact with the ribonucleolytic site residues of angiogenin, whereas the cell binding site and nuclear translocation site residues remain unperturbed. Docked conformations of the synthesized compounds with RNase A and angiogenin suggest a binding preference for the thymine-adenine pair over the thymine-thymine pair.

Synthesis and evaluation of N6-substituted apioadenosines as potential adenosine A3 receptor modulators

“…H 2 SO 4 ) the starting material degraded. Oxidation using RuCl 3 -NaIO 4 , [18] followed by amide coupling, provided 27 and 28 , albeit in very low yield. Removal of the TBDMS groups in 28 gave the desired 3′-ethylcarboxamide 15 .…”

Amino and carboxy functionalized modified nucleosides: A potential class of inhibitors for angiogenin

“…However, these conventional nucleotidic inhibitors have a limited success towards angiogenin compared to RNase A [11], as well as, the high negative charge on the phosphate groups is a great disadvantage regarding their cell permeability [12]. Because of the limited success of the nucleotidic inhibitors different non-nucleosidic molecules are tried on angiogenin [13] and also dinucleosides with amide linkage [14].…”

Acidic‐Amino‐Acid‐Conjugated Dinucleosides as Ribonuclease A Inhibitors: Rational Design and Effect of Backbone Chirality on Enzyme Inhibition

“…Reports on modified dinucleosides with sulfonamide and amide backbones have demonstrated their moderate inhibitory property against RNase A. A recent report has described the triazole double‐headed ribonucleosides as dual inhibitors of RNase A and eosinophil derived neurotoxin (EDN), one of the members of the ribonuclease superfamily.…”

“…Also, electrostatic interactions between the positively charged active site and the negatively charged carboxylate anion were expected to occur under physiological conditions. Consequently, inhibitor 1 and 2 (Figure ) exhibited good inhibitory property against RNase A with low inhibition constants …”

“…An extensive molecular docking study performed on the model inhibitor 1 (Figure ) displayed fewer number of H‐bonding type interactions within the active site of RNase A and the l ‐aspartic derived backbone moved away from catalytic active site P 1 (Figure ). It is known that the understanding of chiral entities at the molecular level provides an insight into diverse areas of drug design and enzyme inhibition.…”