Abstract
The nature and the biochemical mechanism of inhibition of neutrophil membrane-associated oxidative metabolism by two synthetic peptides p77-82 and p201-206 (amino acid sequences Val-Gly-Gly-Ser-Glu-Ile and Lys-Pro-Gln-Leu-Trp-Pro respectively, from the primary amino acid sequence of C-reactive protein) have been ascertained, Preincubating neutrophils for 15 min with 50-mu-M of p77-82 or p201-206 resulted in superoxide generation by opsonized zymosan stimulated neutrophils being inhibited by 34 +/- 2% (P <0.005) and 29 +/- 2% (P <0.005) respectively. With a 60-min preincubation period 6.25-mu-M of p77-82 or p201-206 was effective in inhibiting this superoxide generation by 12 +/- 2% (P <0.01) and 10 +/- 1% (P <0.01) respectively. Neither peptide inhibited neutrophil arachidonic acid release, transmembrane potential or transductional events preceding superoxide generation. Inhibition of neutrophil functions was found to be due to the ability of each peptide (50-mu-M) following a 15-min preincubation period to inhibit both neutrophil glycolysis and ATP generation by approximately 30%. The inhibition of ATP generation and glycolysis in neutrophils is attributable to the ability of these peptides to inhibit uncompetitively the glycolytic enzyme enolase. Using purified enolase the relative Ki values for p77-82 and p201-206 were 27 and 19-mu-M respectively. Inhibition of neutrophil function by the peptides is concluded to be due to effective interference of neutrophil energy metabolism.