The pro‐region of the Kex2 endoprotease of Saccharomyces cerevisiae is removed by self‐processing

We have produced in the baculovirus/insect cells expression system a soluble secreted form of the Saccharomyces cerevisiae Kex2 endoprotease. This secreted enzyme was purified and its NH 2 ‐terminal sequence determined. The NH 2 ‐terminal sequence started at residue Leu 109 of the sequence deduced from the KEX2 gene nucleotide sequence, showing that the Kex2 enzyme is produced as a proenzyme. Residue Leu 109 is preceded by a pair of basic amino acid residues (Lys 107 ‐Arg 108 ) which is a potential processing site for the Kex2 endopeptidase. Futhermore, expression of an inactive form of this truncated enzyme resulted in the production of a protein with a higher molecular weight. These observations suggest that the pro‐region of Kex2 endoprotease is removed by a self‐processing event.