Casual name for small peptides that are potent chemokinetic and chemotactic factors for human leucocytes, particularly neutrophils. The first commonly used example was formyl-methionyl-leucyl-phenyalanine (fMet-Leu-Phe; fMLP), thought to be a synthetic analogue of the bacterial protein start sequence, although the requirement is simply for a formylated N-terminus and usually a hydrophobic amino acid at the C-terminal end. Specific receptors of high affinity are found on human cells but not on those of many domestic animals (e.g. pig, chick). At concentrations around the Kd they elicit locomotory activity, at higher concentrations they stimulate secretion and the metabolic burst.
Subjects: Medicine and Health.