Introduction of non-natural amino acid residues into the substrate-specific P1 position of trypsin inhibitor SFTI-1 yields potent chymotrypsin and cathepsin G inhibitors.
A series of trypsin inhibitor SFTI-1compounds modified in substrate-specific P(1) position was synthesized by the solid-phase method. Lys5 present in the wild inhibitor was replaced by Phe derivatives substituted in para position of the phenyl ring, l-pyridylalanine and N-4-nitrobenzylgycine. Their inhibitory activities with bovine alpha-chymotrypsin and cathepsin G were estimated by determination of association equilibrium constants (K(a)). All analogues inhibited bovine alpha-chymotrypsin. The highest inihbitory activity displayed peptides with the fluorine, nitro and methyl substituents. They were 13-15-fold more active than [Phe(5)]SFTI-1 used as a reference. They are the most potent chymotrypsin inhibitors of this size. Substitution of Lys5 by Phe did not change the cathepsin G inhibitory activity. Introduction of Phe(p-F), Phe(p-NH(2)) and Phe(p-CH(3)) in this position retained the affinity towards this proteinase, whereas Phe(p-guanidine) gave an inhibitor more than twice as active, which appeared to be stable in human serum. On the other hand, a peptomeric analogue with N-4-nitrobenzylglycine failed to inhibit cathepsin G. Despite the fact the introduced amino acids were non-coded, the peptide bonds formed by them were hydrolyzed by chymotrypsin. We postulate that additional interaction of para-substitutents with the enzyme are responsible for the enhanced inhibitory activity of the analogues.
Łegowska
Anna
A
Faculty of Chemistry, University of Gdańsk, Gdańsk, Poland. legowska@chemik.chem.univ.gda.pl
Debowski
Dawid
D
Lesner
Adam
A
Wysocka
Magdalena
M
Rolka
Krzysztof
K
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D056649:Cathepsin G / Q000037:antagonists & inhibitors*; D002417:Cattle; D002918:Chymotrypsin / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000737:chemistry*; D006801:Humans; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000737:chemistry* / Q000494:pharmacology; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D014361:Trypsin Inhibitors / Q000737:chemistry*
D000596:Amino Acids; D004791:Enzyme Inhibitors; D010455:Peptides; D010456:Peptides, Cyclic; C448501:SFTI-1 peptide, sunflower; D014361:Trypsin Inhibitors; D002918:Chymotrypsin; D056649:Cathepsin G