An oral solution containing a mixture of proteinases, which are produced by Streptomyces griseus, with mucolytic activity and potential diagnostic applications. Upon oral administration, pronase is able to cleave peptide chains of polypeptides into individual amino acids, thereby dissolving mucus. The removal of mucus may improve the visibility of parts of the digestive tract, such as the esophagus and the stomach, during endoscopy. Pre-treatment with pronase before endoscopic examination may help in the detection of certain cancers, such as esophageal and gastric cancer.