Fluorescent Derivatives of Polysaccharide Dialdehyde as Substrates for Glucanases

A simple and sensitive assay method for glucanase activity was established using fluorescent polysaccharide substrates. Periodate oxidized α-glucans having dialdehyde were covalently attached to the fluorescent reagent via Schiff base formation followed by NaBH₄ reduction. Ethylenediaminonaphthalene (EDAN) was effective to produce a stable and highly fluorescent polysaccharide. EDAN derivatives of glycogen and dextran dialdehyde were useful substrates for Taka-amylase A and endodextranase, respectively. Two cellulases were shown to release water-soluble fluorescent products from the EDAN derivative of cellulose powder. Moreover, the action of the exo type of enzyme such as glucoamylase was readily distinguished from that of the endo type of enzyme because the attached EDAN prevented the attack of exo-enzyme.