Synthesis and biological activity of analogues of the C-terminal hexapeptide of substance P with modifications at glutaminyl and methioninyl residues. Structure-activity studies.
Analogues of [Orn6]-SP6-11 have been synthesized in which the methionyl residue is replaced by glutamine gamma-carboxamide substituted derivatives. These analogues where tested in three in vitro preparations representative of NK-1, NK-2 and NK-3 receptor types. Substitution of the SCH3 group of the Met11 side chain by CONHCH3, CON(CH3)2, CONHPh and CONCH3Ph groups results in analogues which are full agonists in NK-1 and NK-2 preparations with the exception of the Glu[N(CH3)2]11 and the Glu(NHCH3)11 analogues, which are partial agonists at NK-1 and NK-2 receptors respectively. The Glu(NHCH3)11 analogue shows selectivity for the NK-1 receptor type and is equipotent to the Glu(NCH3Ph)11 analogue in the same receptor type. The latter analogue is 2.84 times more potent than the parent hexapeptide in the NK-2 preparation. The Glu(NHPh)11 analogue is a full agonist in the NK-3 preparation and equipotent to the parent hexapeptide, in contrast to the other analogues in which Met has been replaced by glutamine gamma-carboxamide substituted residues. It is concluded that for NK-1 receptor type the lipophilic character of Met11 side chain is not a determining factor for activity but it is an important factor for activity in the NK-2 receptor type and has a stronger effect when a phenyl group is present, thus leading to analogues which are full agonists and more potent than the parent hexapeptide.
D000595:Amino Acid Sequence; D000818:Animals; D003106:Colon / Q000187:drug effects; D005973:Glutamine; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D008715:Methionine; D008969:Molecular Sequence Data; D009130:Muscle, Smooth / Q000187:drug effects; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology; D011169:Portal Vein / Q000187:drug effects; D051381:Rats; D018041:Receptors, Neurokinin-2; D017981:Receptors, Neurotransmitter / Q000187:drug effects*; D013329:Structure-Activity Relationship; D013373:Substance P / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology
D010446:Peptide Fragments; D018041:Receptors, Neurokinin-2; D017981:Receptors, Neurotransmitter; D005973:Glutamine; C079225:substance P (6-11), Orn(6)-; D013373:Substance P; D008715:Methionine