Evidence for the presence of proteolytic activity in peroxisomes

The presence of endo- and exoproteolytic activity in peroxisomes was detected in cell organelles purified from pea leaves. By PAGE using different exopeptidase substrates (L-aa-beta NA), one leucine aminopeptidase (AP) was found in peroxisomes. The peroxisomal AP was characterized as a serine protease and had a maximal activity at pH 7.5, a molecular mass of 56.8 kDa and a pI of 5.3. This enzyme was mainly present in the soluble fraction of peroxisomes. The occurrence of proteases in peroxisomes suggests that they might be involved in the protein turnover and processing of imported precursor polypeptides in peroxisomes.