The present invention relates to a protease variant which is at least 90% identical to the full length amino acid sequence of a Kumamolisin AS backbone as set forth in any of SEQ ID NOs 1 - 3, while maintaining proteolytic activity, or a fragment, fraction or shuffled variant thereof maintaining proteolytic activity, which protease variant demonstrates altered or improved stability compared to theKumamolisin AS wildtype as set forth in SEQ ID NO 4, or the Kumamolisin AS backbone as set forth in any of SEQ ID NOs 1 - 3.