Zingibain, zingipain, or ginger protease (EC 3.4.22.67) is a cysteine protease enzyme found in ginger (Zingiber officinale) rhizomes. It catalyses the preferential cleavage of peptides with a proline residue at the P2 position. It has two distinct forms, ginger protease I (GP-I) and ginger protease II (GP-II). It was first isolated, purified, and reported in 1973 by Ichikawa et al. at Japan Women's University. Recently, zingibain was found to exist as two isozymes, GP-I and GP-II, which were isolated by chromatography, with molecular weights of approximately 22,500 Da.