Isolation and partial characterization of pigeon pea protease inhibitor: its effect on the genotoxic action of aflatoxin B1.

Protease inhibitor was isolated and purified from pigeon pea Cajanus capan. By using gel filtration analysis the inhibitor was found to have an Mr of 18,200. It inhibits trypsin competitively with a specific inhibitor constant Ki of 1.53 x 10(-7) M. The purified inhibitor produced a marked reduction in aflatoxin B1-induced beta-galactosidase activity in Escherichia coli PQ37. This reduction is independent of whether the protease inhibitor was added to the reaction medium prior to or after aflatoxin B1 activation. The observed reduction may therefore be a result of the inhibitor's activity on the RecA protease produced in response to aflatoxin B1-induced DNA damage in the bacteria.