This assay procedure is specific for endo-acting pullulanase and limit-dextrinase (from grain) activity. On incubation of Red-Pullulan with pullulanase or limit-dextrinase the substrate is depolymerised by an endo-mechanism to produce lowmolecular-weight dyed fragments which remain in solution on addition of ethanol to the reaction mixture. High-molecular weight material is removed by centrifugation, and the colour of the supernatant is measured at 510 nm. Pullulanase in the assay solution is determined by reference to a standard curve. Although this substrate can be used to measure limit-dextrinase, we recommend the use of Limit-Dextrizyme tablets (cat. no.T-LDZ) which form the basis of an assay with a greater sensitivity.