Subcellular Localization of Rice Leaf Aryl Acylamidase Activity

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Abstract
The intracellular localization of aryl acylamidase (aryl-acylamide amidohydrolase, EC 3.5.1.13) in rice (Oryza sativa L. cv. Starbonnet) leaves was investigated. The enzyme hydrolyzes and detoxifies the herbicide propanil (3,4-dichloropropionanilide) thereby accounting for immunity of the rice plant to herbicidal action. Fractionation of mesophyll protoplasts by differential centrifugation yielded the highest specific activity of amidase in the crude mitochondria fraction. Further separation of density gradients of the silica sol Percoll also indicated that this enzyme was mitochondrial. The use of biochemical markers showed that the purified mitochondrial fraction was substantially free of contamination from nuclei, chloroplasts, golgi and plasma membranes. Subfractionation of the purified mitochondria suggests that this enzyme is located on the outer membrane.