Abstract
Incubation of human serum with cobra or viper venoms ( 10 μ g 0.1 ml serum) caused negligible decrease in total protease inhibitory activity whereas α 2-macroglobulin activity was reduced by 67.0–82.0% in 16 hr. The action of venoms on MG activity was time dependent. Human α 2-macroglobulin activity was reduced to a much greater extent than goat or bovine factors by the venoms. While 25 μ g venoms 0.1 ml serum caused 60–100% inhibition of human α 2-macroglobulin activity, the bovine factor was not affected under similar conditions. Goat α 2-macroglobulin was affected to the extent of 0–20%. Evidence is provided to show that venom proteases generate endogenous proteases in situ in human plasma or serum which in turn bind to α 2-macroglobulin. The venom-mediated action was abolished by prior dialysis of the serum or its dilution. Ethylenediaminetetraacetate at 10 −3 m concentration also blocked the reaction. While phenylmethylsulfonyl fluoride had no effect, pepstatin in the concentration range 10 −2 to 10 −3 m caused partial inhibition of the venom-mediated inhibition of α 2-macroglobulin activity in human serum.
Published Version
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