Figure 2.

Reaction curves for the validation of the α- and β-maltose NADP-linked spectrophotometric assay. A, Sequential measurement of α- and β-maltose was achieved by adding maltose phosphorylase, then maltose epimerase to a reaction mixture that contained 650 pmol of commercially obtained maltose. B, β-Maltose produced by the action of β-amylase on 125 pmol maltoheptose (G7) was not acted on by maltose phosphorylase until maltose epimerase was added. A change in OD is observed only when maltose epimerase is added to the reaction mixture, demonstrating that maltose phosphorylase is specific for the α-anomer. In both A and B, Glc-6-P dehydrogenase and hexokinase were already added to the reaction mixture. MPL, Maltose phosphorylase; MER, maltose epimerase; β-Amy, β-amylase. Horizontal bar = 2 min in both A and B; vertical bar = 0.00092 OD units or 100 pmol under our assay conditions in both A and B.