Selective inhibition of microbial serine proteases by eNAP-2, an antimicrobial peptide from equine neutrophils.
Equine neutrophil antimicrobial peptide 2 (eNAP-2), a recently described antimicrobial peptide isolated from equine neutrophils, was found to selectively inactivate microbial serine proteases (subtilisin A and proteinase K) without inhibiting mammalian serine proteases (human neutrophil elastase, human cathepsin G, and bovine pancreatic trypsin). Although the primary structure of eNAP-2 resembled that of several known antiproteases that belong to the 4-disulfide core peptide family, this pattern of selectivity is unique. eNAP-2 formed a noncovalent complex with native subtilisin A or proteinase K but did not associate with these enzymes if they had been treated with phenylmethylsulfonyl fluoride, a serine protease inhibitor. The eNAP-2-microbial protease complex was disrupted by boiling or by exposure to low pH. We suggest that eNAP-2 exerted selective antiproteinase activity by binding tightly but noncovalently to the active site of subtilisin A or proteinase K. Since microbial exoproteases may act as virulence factors, the combined antimicrobial and antiprotease activities of eNAP-2 could allow it to play an important role in neutrophil-mediated antimicrobial defenses.
Couto
M A
MA
Department of Medicine, UCLA School of Medicine 90024.
Harwig
S S
SS
Lehrer
R I
RI
D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology*; D001798:Blood Proteins / Q000494:pharmacology*; D019286:Endopeptidase K; D006736:Horses; D009504:Neutrophils / Q000737:chemistry*; D012697:Serine Endopeptidases / Q000378:metabolism; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology*; D013381:Subtilisins / Q000037:antagonists & inhibitors
D000890:Anti-Infective Agents; D001798:Blood Proteins; D015842:Serine Proteinase Inhibitors; C078461:equine neutrophil antibiotic peptide 2; D012697:Serine Endopeptidases; D013381:Subtilisins; D019286:Endopeptidase K