Aspergillopepsin II

Aspergilloglutamic peptidase, also called aspergillopepsin II (EC 3.4.23.19, proctase A, Aspergillus niger acid proteinase A, Aspergillus niger var. macrosporus aspartic proteinase) is a proteolytic enzyme. The enzyme was previously thought be an aspartic protease, but it was later shown to be a glutamic protease with a catalytic Glu residue at the active site, and was therefore renamed aspergilloglutamic peptidase.

Determination of its molecular structure showed it to be a unique two-chain enzyme with a light chain and a heavy chain bound non-covalently with each other. The C-terminal region of the light chain of one molecule binds to the active site cleft of another molecule in the manner of a substrate.

This enzyme catalyses the following chemical reaction

Preferential cleavage in B chain of insulin: Asn³-Gln, Gly1³-Ala, Tyr²⁶-Thr

This enzyme is isolated from Aspergillus niger var. macrosporus.