Proteinase activities in bovine atrium and the possible role of mast cell tryptase in the processing of Atrial Natriuretic Factor (ANF)

Abstract

1. 1. Using low salt, Triton X-100 and high salt extracts of bovine atria, two main proteinases were identified by means of fluorogenic oligopeptide substrates. 2. 2. An acidic proteinase, extracted in low salt and Triton X-100 was identified as cathepsin B, but it caused little hydrolysis of the Z-Gly-Pro-Arg-containing substrate that resembles the cleavage site for activation of pro-ANF. 3. 3. An alkaline proteinase was extracted only with high salt and had characteristics of the serine proteinase tryptase. It cleaved Z-Gly-Pro-Arg-containing substrates more efficiently than others tested and was localized in and around mast cells histochemically. Previously, Imada et al., 1988 ( J. biol. Chem. 263, 9515–9519) found an identical enzyme would cleave ANF from pro-ANF. 4. 4. These results suggest therefore that mast cell typtase may be involved in the activation of ANF from pro-ANF.