Myrosinase in Brassicaceae (Cruciferae)

Abstract

Seeds of Sinapis alba L. were germinated in darkness for 3 d and a part of the etiolated seedlings were transferred to long-day conditions for 6 weeks. Myrosinase solutions were prepared for cotyledons, hypocotyls, primary roots, leaves, stems, inflorescences, and seeds, and used to hydrolyse sinigrin. Glucose, one of the cleavage products, was determined by four different spectrophotometric methods, and their usefulness for calculations of myrosinase activity in crude plant extracts is considered. Specific activity was calculated in relations to protein, and it was found to be about 30% higher in seedlings and also higher in seeds than in adult plants. Of the organs, those with the highest activity were the hypocotyls and the stems. The different parts of the plant contained different numbers of isoenzymes, as shown by polyacrylamide gel electrophoresis. Seedlings yielded two, and adult plants four or five isoenzymes.