Aspartic protease. Cleaves alpha-lactalbumin but not beta-lactoglobulin. Inhibited by the specific aspartic proteinase inhibitors diazoacetyl-noleucine methyl ester and pepstatin. Optimum pH is 5.0. Active from pH 2.0-7.0. Stable at temperatures of up to 60 degrees Celsius. Heterodimer of a light chain and a heavy chain. An intermediate form is produced first, and undergoes proteolytic processing to remove the internal plant-specific insert (PSI) and the propeptide. Procardosin-B is associated with the microsomal membranes, the mature form is secreted. Detected in pistils, but not in seeds, bracts, midribs, roots, leaves or stamen extracts (PubMed:11414612). Detected in seeds (PubMed:18767217). In stigmas and styles, detected in the transmitting tissue and in contiguous subepidermal layers at the longitudenal grooves of the stigma (at protein level). In flowers, highest levels of mRNA are found in closed capitula and amount decreases during floral development, detected at protein level in both closed and open flowers. At the mRNA level, virtually undetectable in seeds at all stages. At protein level, detected in the embryo during the first stages after seed hydration, levels gradually decrease and it becomes almost undetectable after 72-84 hours. Belongs to the peptidase A1 family.