New chelator-sensitive proteases in matrix of yeast mitochondria

Proteases in yeast mitochondria were studied using fluorogenic synthetic substrates containing methylcoumaryl amide (MCA). Among the eleven substrates which are commonly employed for several types of proteases, Leu-MCA, Arg-MCA, Boc-Gln-Arg-Arg-MCA and Boc-Phe-Ser-Arg-MCA were found to be highly susceptible to proteases in mitochondria. All these proteases were localized in the matrix and sensitive to o-phenanthroline but not to phenylmethylsulfonyl fluoride or iodoacetate. The analysis of hydrolyzed products of Boc-Gln-Arg-Arg-MCA indicated that the peptide was cleaved at the site between Gln and Arg. These results demonstrate that there exist chelator-sensitive aminopeptidase(s) and endopeptidases in the matrix of yeast mitochondria.