Mechanism of Cleavage of Rabbit IgG in Two Stages by Soluble Papain and Reducing Agent

[摘要] The mechanism of an apparent two-stage cleavage of rabbit IgG by soluble papain and L-cysteine was investigated. In the absence of reducing agent papain had no detectable effect on the sedimentation velocity or precipitating activity of antibody. After treatment with iodoacetamide and gel filtration, in an effort to inactivate and remove papain, addition of reducing agent resulted in cleavage into univalent 3.5 S fragments. This was shown to be attributable to partial resistance of papain to alkylation, particularly in the presence of IgG, and to adherence of an appreciable quantity of the enzyme to IgG during gel filtration. The results are consistent with a mechanism in which papain acts through cleavage of the heavy chains, and in which the reducing agent activates the enzyme but does not necessarily act directly on the IgG molecule.

[学科分类] 生物科学（综合）