The present invention deals with the proteolytic enzyme thermolysin which tends to be unstable in aqueous solution. The invention provides methods and compositions to enhance the stability of dissolved thermolysin in aqueous solution. Thermolysin, crude thermolysin or a lyophilisate containing thermolysin and one or more salts, is contacted with an aqueous buffer with a low salt concentration and a first solution is formed. Subsequently, a further salt in solid form is added and dissociated, thereby forming a second solution comprising thermolysin in a stabilized form.