Multiple forms of the asclepains. Cysteinyl proteases from milkweed.

Two groups of asclepains (EC 3.4.22.7) isolated from the latex of Asclepias syriaca L. (milkweed) were each separated into five homogeneous enzymes. The members of each group are of similar amino acid composition, and leucine is the common N-terminal residue. Michaelis values are reported for each of the component cysteinyl proteases of milkweek latex, and are compared with those of analogous enzymes from other plant sources. The asclepains all catalysed the hydrolysis of insulin B chain to yield similar two-dimensional maps. The peptides produced from one such digestion were characterized and scission points were defined and compared with those for papain.