Purification of a specific peptidase in bovine atria for the processing of pro-atrial natriuretic factor

A serine protease which catalyses the conversion of the precursor of ANF (atrial natriuretic factor) to the active circulating form, ANF-(99-126)-octacosapeptide, was purified from a particulate fraction of bovine atria. The enzyme was solubilized with a buffer containing 1.6M KCl. The molecular mass of the purified enzyme was 580 kDa on gel filtration, whereas on sodium dodecyl sulfate-polyacrylamide gel electrophoresis a cluster of six bands with molecular masses around 30 kDa was observed. The purified enzyme produced the ANF-(99-126)-octacosapeptide from partially purified bovine pro-ANF by the selective cleavage of the arginyl peptide bond in the -Pro97-Arg98-Ser99-sequence in pro-ANF. It is likely that the enzyme selectively cleaves the Arg98-Ser99 peptide bond in pro-ANF when ANF is secreted into the circulation.