An aryl acylamidase from tulip which hydrolyzes 3′,4′-dichloropropionanilide

An aryl acylamidase which hydrolyzes the herbicide propanil (3′,4′-dichloropropionanilide), has been isolated from tulip bulbs and partially purified and characterized. Several chlorinated ring-substituted propionanilide analogs as well as 3,4-dichloroacetanilide and 3′,4′-dichloro-2-methacrylanilide (dicryl) were hydrolyzed by the enzyme. The partially purified enzyme lacked sensitive-SH groups and possessed a broad pH optimum between 6·8 and 7·8. The enzyme was relatively stable up to about 50°, but lost activity rapidly on exposure to temperatures above this. The optimum temperature of assay with 3′,4′-dichloropropionanilide was 53°. The apparent activation energy of the enzyme was 10·3 kcal/mole and the apparent Km was 2·50 × 10−3m, with 3′,4′-dichloropropionanilide as substrate. The properties of this acylamidase from tulip were compared with aryl acylamidases from rice and liver.