May represent a new class of acid proteases. It digests proteins and peptides in acidic solution. Specificity similar to pepsin A, prefers bulky hydrophobic side-chains on either side of the scissible bond. Optimum pH is 2. Optimum temperature is 90 degrees Celsius. Thermostable. May be linked to cells by covalent linkages through some side chains. Belongs to the peptidase A5 family.