1-Substituted sialorphin analogues—synthesis, molecular modelling and in vitro effect on enkephalins degradation by NEP

Abstract

Rat sialorphin (Gln-His-Asn-Pro-Arg) is a natural blocker of neprilysin (NEP) that belongs to the family of endogenous opioid peptide-degrading enzymes. Studies have confirmed the efficiency of sialorphin in blocking the activity of NEP, both in vitro and in vivo. It has been demonstrated that this inhibitor has a strong analgesic, anti-inflammatory, immunological and metabolic effect either directly or indirectly by affecting the level of Met/Leu-enkephalins. In this work, sialorphin and their 12 analogues were synthesised using the solid-phase method. The effect of the peptides on the degradation of Metenkephalin by NEP and metabolic degradation in human plasma was investigated in vitro. We show that the change in the N-terminal amino acid configuration from l to d in almost all peptides, except d-Arg-His-Asn-Pro-Arg (peptide XI), led to the abolition of their inhibitory activity. With molecular modelling technique we explained the structural properties of the l and d-arginine located on the N-terminal part of the peptide. The detailed analysis of the protein binding pocket allowed us to explain why d-arginine is so unique among all d residues. Peptide XI showed the highest stability among the tested peptides in human plasma. For instance sialorphin after a 2-hour incubation in human plasma was almost completely decomposed, while the level of peptide XI dropped to 45% after 48 h under these conditions.

Anti-Inflammatory Effect of Homo- and Heterodimers of Natural Enkephalinase Inhibitors in Experimental Colitis in Mice

“…Plasma-stability assays were performed, as described previously [21]. The sample preparation and the analysis of peptide I were both performed in the same way as in our previous work [21].…”

“…Plasma-stability assays were performed, as described previously [21]. The sample preparation and the analysis of peptide I were both performed in the same way as in our previous work [21]. Peptides III and X were analyzed by RP-HPLC using a linear gradient of 20-80% B over 20 min with the same solvent system of 0.1% TFA in water (A) and 0.1% TFA in acetonitrile (B), with a flow rate of 1.5 mL/min.…”

“…The means of the % of remaining peptide with a standard deviation are presented. * data published in Sobocinska et al[21].…”

“…The small amount of opiorphin (12%) disappears because of potential complex formation [20]. Sialorphin is also sensitive to degradation in human plasma [21].…”

Peptide late-stage C(sp3)–H arylation by native asparagine assistance without exogenous directing groups

“…Therefore, we introduce Asn as an internal bidentate DG to accomplish C(sp 3 )-H activation of peptides. Simultaneously, Asn is a common residue contained in many bioactive peptides, which display a range of biological activities, such as antioxidant activity, 18 blocking the neprilysin activity, 19 and inhibiting ACE activity. 20 Remarkably, Phe-Asn is an essential sequence that exists in some bioactive peptides, for example novel ACE inhibitory peptides, 21 anticancer peptides, 22 and AGRP.…”