Isolation and Characterization of Xanthium Lipase

Abstract

The fruit of the Xanthium sp. (cocklebur) contains two seeds; one is a large, non-dormant seed and the other is a small, dormant seed. Dormancy in the small seed can be broken and germination promoted by the presence or kinetin and light (9). Because an early event in the germination of seed involves the hydrolysis of stored foods, light and kinetin possibly interact to promote the synthesis or activation of specific hydrolytic enzymes, which in turn initiate the degradation of food reserves to supply energy for the germination process. Khan {9) has shown that inhibition of DNA-dependent RNA synthesis reverses the effect of kinetin and light, so synthesis of one or more enzymes may be required for the breaking of dormancy in cocklebur seeds, Since preliminary investigation showed that the principle food-storage material in cocklebur seeds is lipid, and because there is some evidence that light is important in the synthesis of lipase, it was decided to compare the development of lipase activity in germinating large and small seeds to determine whether lipase synthesis or activation is a primary event in the breaking of cocklebur dormancy.

Published procedures for the isolation of seed lipase were found not to be applicable to cocklebur seed. As a result, it was necessary to develop analytical methods for the study of cocklebur lipase. This paper will present isolation methods and characteristics of the lipase found in germinating large cocklebur seed.