Characterization and mechanism of action of Microbacterium imperiale glucan 1,4-α-maltotriohydrolase

•Glucan 1,4-α-maltotriohydrolase (AMTS) is an enzyme that catalyzes transglycosylation reactions.•AMTS transfers maltotriosyl units.•The smallest donor of transglycosylation reactions by AMTS is maltotetraose.•Maltotriose production is controlled by starch structure and hydrolysis time.

In this study, glucan 1,4-α-maltotriohydrolase (AMTS) from Microbacterium imperiale was purified and characterized. Hydrolysis by AMTS was affected by starch structure (e.g., amylose versus amylopectin) and hydrolysis time. During the initial phase of hydrolysis of maltooligosaccharides (G4–G7), AMTS displayed a unique transfer specificity to the transfer of maltotriosyl units. After extensive hydrolysis, maltotriose became the major end product, followed by glucose and maltose. Maltotetraose (G4) was the smallest donor in transglycosylation reactions by AMTS. This is the first study that reports transglycosylation activity of AMTS on maltooligosaccharides. The results of this study suggest that high purity maltotriose can be produced by the hydrolytic action of AMTS on starch.

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