Ragweed pollen proteolytic enzymes: Possible roles in allergies and asthma

Abstract

Extracts from ragweed pollen grains contain novel trypsin and chymotrypsin-like serine peptidases which are described in this report. The molecular mass of the chymotrypsin-like enzyme was 82 kDa, had a pH optimum near 9.0, and its activity was unaffected by chelating or reducing agents. It was inhibited by diisopropyl fluorophosphate (DFP), a general serine class inhibitor, and more specifically N-p- tosyl- l - phenylalanine chloromethyl ketone (TPCK), a chymotrypsin-like proteinase inhibitor. In addition to various synthetic substrates, the neuropeptides, vasoactive intestinal peptide (VIP) and substance P, which are required for normalized lung functions, were also rapidly hydrolysed. Activity toward protein substrates was not detected with the exception of the inactivation of α-1-proteinase inhibitor (α-1-PI) which occurred through cleavage within the reactive site loop. The ‘trypsin-like’ enzyme has a molecular mass near 80 kDa, a blocked N-terminus, a pH optimum near 9.0, and requires Ca ++ for stability and activity, but not reducing agents. It is inhibited by DFP, and more specifically the trypsin-like proteinase inhibitor, N-p- tosyl- l - lysine chloromethyl ketone (TLCK). Again, activity toward protein substrates was not detected, but various synthetic substrates and biologically active peptides were efficiently cleaved. Significantly, atrial natriuretic peptide (ANP) and angiotensin 2 (ATII), whose degradation would amplify kinin activity and influence inflammatory diseases of the respiratory tract and nasal passages, were also rapidly hydrolyzed.