Rhizopuspepsin (EC 3.4.23.21, Rhizopus aspartic proteinase, neurase, Rhizopus acid protease, Rhizopus acid proteinase) is an enzyme. This enzyme catalyses the following chemical reaction Rhizopuspepsin (EC 3.4.23.21, Rhizopus aspartic proteinase, neurase, Rhizopus acid protease, Rhizopus acid proteinase) is an enzyme. This enzyme catalyses the following chemical reaction From the zygomycete fungus Rhizopus chinensis. A similar endopeptidase is found in R. niveus . In peptidase family A1 (pepsin A family).