A cysteine proteinase obtained from the fruit of Pileus mexicanus probably identical with Leucopremna mexicana (A.DC.) Standl., Caricaceae: Castaneda-Agullo et al., Science 96, 365 (1942); J. Biol. Chem. 159, 751 (1945). Immunological studies: Estrada-Parra et al., Rev. Latinoam. Microbiol. Parasitol. 1969, 145, C.A. 72, 1744u (1970). Mol wt about 31,100; lysine and alanine believed to be the N- and C-terminal amino acids resp: Soriano et al., Rev. Latinoam. Quim. 1975, 143, C.A. 84, 56489t (1976).