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An enzyme (R-enzyme), which catalyses the scission of branch links in amylopectin, has been isolated from the potato and the broad bean as a stable amorphous powder.It is shown that R-enzyme operates by a purely hydrolytic process and that, unlike Q-enzyme, it has no link-synthesising function. It is a " debranching " enzyme with respect to the predominant type of branch linkage in amylopectin, the 1 : 6-glucosidic link. It neither makes nor breaks chain-forming 1 : 4-links and has no action on amylose (synthetic or natural) or on the linear dextrins related to amylose.A convenient method of estimating the activity of R-enzyme is based on the fact that its action on amylopectin or limit P-dextrin is accompanied by a rise in the iodine-staining power of the substrate.' with potato starch. When treated in this way, the Q-preparation lost its a-amylolytic activity but, what was more

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Baker's yeast glucan has been partly hydrolysed with acid, and the products have been fractionated on charcoal-Celite. Eight mono-, di-, tri-, and tetra-saccharides, considered to be fragments of the glucan molecule, have been isolated and identified. These are D-glucose, gentiobiose, laminaribiose, gentiotriose, 6-O-~-laminaribiosylglucose, laminaritriose, 3-O-P-gentiobiosylglucose, and gentiotetraose. It is concluded that the glucan is a linear polymer of p-D-glucopyranose in which 1 : 3-and 1 : 6-linkages are arranged at random or in sequences such that a group of a t least three 1 : 6linkages is flanked on either side by 1 : 3-linkages. Periodate-oxidation results suggest that the combined proportion of non-reducing end groups and 1 : 6-links is 1 per 10 glucose residues.

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