N-terminal modifications of selected formyl peptides and effects on agonistic activity Most of the early studies were conducted using neutrophils from rabbits and humans. Note that the concentration of formyl peptides required for superoxide production and enzyme release is 10- to 50-fold higher than the concentration needed for maximal chemotaxis. Therefore, caution should be taken when comparing potency using different assays. Some variations may also exist between assays conducted in different laboratories.

Ligand Assay Effects Potency References
N-formyl-Met-Leu-Phe Chemotaxis Agonistic pEC50 = 10.15 Freer et al. (1980); Showell et al. (1976)
Met-Leu-Phe Chemotaxis Agonistic pEC50 = 6.17 Showell et al. (1976)
N-acetyl-Met-Leu-Phe Chemotaxis Agonistic pEC50 = 6.70 Freer et al. (1980)
N-p-tolylurea-Met-Leu-Phe Embedded Image production Agonistic pEC50 = 8.70 Higgins et al. (1996)
N-tert-butyloxycarbonyl-Met-Leu-Phe Enzyme release Antagonistic pIC50 = 6.19 Freer et al. (1980)
N-iso-butyloxycarbonyl-Met-Leu-Phe Embedded Image production Antagonistic pIC50 = 6.60 Derian et al. (1996)
N-formyl-Met-Phe-Leu Chemotaxis Agonistic pEC50 = 7.27 Showell et al. (1976)
Met-Phe-Leu Chemotaxis Agonistic pEC50 = 3.62 Showell et al. (1976)
N-acetyl-Met-Nle-Leu-Phe-Phe Ca2+ flux Agonistic pEC50 = 10.00 Gao et al. (1994)
N-formyl-Met-Nle-Leu-Phe-Phe Ca2+ flux Agonistic pEC50 = 10.00 Gao et al. (1994)
Met-Nle-Leu-Phe-Phe Ca2+ flux Agonistic pEC50 = 9.00 Gao et al. (1994)
  • pIC50, negative logarithm of the IC50; pEC50, negative logarithm of the EC50; pKd, negative logarithm of Kd