A novel and direct assay for measuring enzymatic depolymerisation of beta-1,3-glucans

Indirect colorimetric analyses of released reducing groups, as an indicator of induced beta-1,3-glucanase activities, tend to be the assay methods of choice for the characterization of plant endo- and exo-beta-1,3-glucanase, However, interfering low molecular weight reducing sugars found in unproces sed plant extracts often mask in vitro estimations of P-ld-glucanase activi ty. The enzyme-catalysed hydrolysis of an optically active beta-1,3-glucan polymer was monitored polarimetrically by measuring changes in the rotation of plane-polarized light of the reaction assay medium. A direct, non-radio chemical assay that detects changes in the optical rotation of released (1- >3) beta-D-oligoglucosides with low degrees of polymerisation (<<25) has be en found to be highly reproducible, rapid (total analysis time 15 min), sen sitive (detection limit 0.007 unit/mL glucanase), selective and non-destruc tive. This assay has been used to detect a salicylate-induced cell wall-bou nd tomato beta-1,3-glucanase, which is a component of a pathogenesis-relate d response in plants. Copyright (C) 2000 John Wiley & Sons, Ltd.