摘要：Activation of Rhizopus delemar C-lipase activity toward tripropionin by DDT and aldrin was studied by using a purified enzyme preparation. Titration experiments of lipase with the pesticide indicated that two molecules of the pesticides first bind to the lipase molecule without activation of the enzyme activity, but this binding facilitates the binding of further pesticide molecules to afford highly active pesticide-lipase complexes, a 9 : 1 DDT-lipase complex and a 7 : 1 aldrin-lipase complex, with 4.4 times and 16 times the activity of intact lipase, respectively. Polyacrylamide gel electrophoresis resolved the intact lipase and the pesticide-lipase complexes, giving each as a distinct protein band, suggesting the formation of irreversibly bound complexes. Gel filtration results also supported this hypothesis. The titration experiments also suggested that the binding of the first two molecules of the pesticides occurs at different specific sites of the lipase molecule for DDT and aldrin, influencing the nature of the enzyme ; the binding of the first two DDT molecules resulted in the formation of a DDT-activated complex, while treatment of the intact lipase with a mixture of DDT and aldrin gave an aldrin-activated complex.
