The partial purification and some properties of two sucrases of Phaseolus vulgaris

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Abstract
Two sucrases present in P. vulgaris were easily differentiated, one, apparently specific for sucrose, with optimum pH 7.7 (named alkaline sucrase) and the other (shown to be a [beta]B-fructofuranosidase) with optimum pH 5.0. Alkaline sucrase was present in the ungerminated seed. [beta]B -Fructofuranosidase was absent from the ungerminated seed but appeared in the embryo on germination, reaching a maximum (under etiolated conditions) after 9-10 days. Much of the activity appeared in the roots. The alkaline sucrase could be purified only 2-fold, whereas the [beta]B-fructofuranosidase was purified 110-fold. The Km for the [beta]B-fructofuranosidase was 2.4 m[image] on sucrose and 14 m[image] on raffinose. Alkaline sucrase had Km 8.9 m[image] on sucrose. Both enzymes were inhibited by Ag+ ions (0.1 m[image]), though iodoacetamide (10 m[image]) had little effect. Alkaline sucrase was strongly inhibited by tris. Transferase activity was observed with the B-fructofuranosidase but not with alkaline sucrase. The function of the sucrases in vivo and their relation to the metabolism of raffinose-type oligosaccharides during germination is discussed.