HPAEC-PAD and Q-TOF-MS/MS analysis reveal a novel mode of action of endo-β-1,3(4)-d-glucanase Eng16A from coprinopsis cinerea on barley β-glucan.

Highlights • Q-TOF-MS/MS analysis reveals a novel mode of Eng16A action on barley β-glucan. • Eng16A can cleave (1 → 4)-β-linkages adjacent to two sides of the (1 → 3)-β-linkage. • Insertion of a (1 → 3)-β-linkage makes (1 → 4)-β-linkages prone to cleavage by Eng16A. Abstract We previously reported that an endo-β-1,3(4)- d -glucanase, Eng16A, from C. cinerea shows a higher degradation activity toward barley β-glucan than laminarin. HPAEC-PAD and Q-TOF-MS/MS analyses show that Eng16A-digestion products of barley β-glucan not only contain some oligosaccharides with (1 → 3)-β-linkage adjacent to the reducing end, which is consistent with β-1,3(4)-glucanase-digestion products, but also include some oligosaccharides containing (1 → 4)-β-linkage adjacent to the reducing end which is consistent with cellulase-digestion products. Thus, Eng16A possesses both cellulase and β-1,3(4)-glucanase activities. Because Eng16A does not degrade cellulose, we propose that the insertion of a (1 → 3)-β-linkage among the groups of (1 → 4)-β-linkages may make these (1 → 4)-β-linkages prone to cleavage by Eng16A. Furthermore, Eng16A also possesses transglycosylation activity which leads to some products containing one or a few consecutive (1 → 3)-β-linkages adjacent to the non-reducing end. Therefore, HPAEC-PAD and Q-TOF-MS/MS analyses provide an efficient approach to reveal complicated modes of action of some endo-β-1,3(4)- d -glucanases on barley β-glucan. [ABSTRACT FROM AUTHOR]