Am. J. Respir. Cell Mol. Biol.,
Volume 18, Number 3, March, 1998 363-369
Purification and Characterization of an Arginine-specific Peptidase
from Ragweed (Ambrosia artemisiifolia) Pollen
Dennis A.
Bagarozzi Jr.,
Jan
Potempa,
and
James
Travis
Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia; and Department of
Microbiology and Immunology, Institute of Molecular Biology, Jagiellonian University, Krakow, Poland
Ragweed (Ambrosia artemisiifolia) is clinically the most important source of seasonal aeroallergens, as it
is responsible for the majority and most severe cases of hay fever (allergic rhinitis). Extracts from pollen
grains have been shown to contain numerous proteins with various functions, including a novel serine proteolytic enzyme with chymotrypsin-like specificity that has been previously described (J. Biol. Chem.
1996; 271:26227-26232). We now report the isolation and properties of a second, trypsin-like enzyme
with a molecular mass near 80 kD, from ragweed pollen extracts. This enzyme has a blocked N-terminus,
a pH optimum near 9.0, and requires Ca2+ for stability and activity, but not reducing agents. The enzyme is
inhibited by diisopropyl fluorophosphate, a general serine class proteinase inhibitor, and more specifically
by N-p-tosyl-L-lysine chloromethyl ketone. Activity toward protein substrates was not detected, but various synthetic substrates and small biologically active peptides were efficiently cleaved, with a strong preference for Arg in the P1 position and either Arg or Gly in the P2 position. This specificity was confirmed
through inhibition studies with both peptidyl chloromethyl ketone and organophosphate inhibitors. Significantly, atrial natriuretic peptide and angiotensin 2, whose degradation would amplify kinin activity and influence inflammatory diseases of the respiratory tract and nasal passages, were also rapidly hydrolyzed.
Thus, the ragweed pollen endopeptidase may be involved in the inactivation of regulatory neuropeptides
during pollen-initiated allergic reactions.
