Amylopectin alpha-amylase action

The presence of phosphorus in amylopectin samples also produces a barrier to the action of alpha-amylase. Small dextrins are formed that contain phosphate groups and unattacked a -D-(l- 4)-linkages. The blocking action of the phosphate groups is, presumably, due to steric hindrance at C-6. 

Another common method for determination of alpha-samylase involves measurement of the diminution of the iodine-stainability of whole starch or amylopectin )8-limit dextrin. These methods are useful, as very small quantities of alpha-amylase may be estimated in this way. They are comparative, and cannot be used to determine rates of bond scission, unless they are carefully calibrated by a method that measures reducing end-groups. Such a calibration has been made for the action of hog-pancreas alpha-amylase on waxy-maize starch, although the validity of the reducing-power determinations, made with iodine and thiosulfate, has been confirmed for maltose only thus, it is not yet known whether the calibration is actually valid for the experimental system in which larger oligomers, for example, the triose and tetraose, are also formed. 

At the concentration used, debranching of amylopectin and its beta-limit dextrin was incomplete, and there was no action on glycogen. First-stage, alpha-amylase limit-dextrins, those containing side chains of... 

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