Characterization of a proteolytic enzyme in the skin secretions of Xenopus laevis

Enzymes present in the skin secretions of Xenopus laevis were fractionated by ion exchange chromatography. One of the proteases obtained was found to catalyse cleavage on the COOH-side of peptide sequences containing consecutive hydrophobic and basic residues. Evidence is presented that the enzyme is a cysteine protease with an optimum pH of 5.0 to 6.0. The characteristic specificity of this enzyme suggests that it may fulfil a role in propeptide processing.