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Effects of Mutation of Asn694 in Aspergillus Niger α-glucosidase on Hydrolysis and Transglucosylation

Effects of Mutation of Asn694 in Aspergillus Niger α-glucosidase on Hydrolysis and Transglucosylation

Min Ma, Masayuki Okuyama, Megumi Sato, Takayoshi Tagami, Patcharapa Klahan, Yuya Kumagai, Haruhide Mori, Atsuo Kimura

Appl Microbiol Biotechnol. 2017 Aug;101(16):6399-6408.

PMID: 28688044

Abstract:

Aspergillus niger α-glucosidase (ANG), a member of glycoside hydrolase family 31, catalyzes hydrolysis of α-glucosidic linkages at the non-reducing end. In the presence of high concentrations of maltose, the enzyme also catalyzes the formation of α-(1→6)-glucosyl products by transglucosylation and it is used for production of the industrially useful panose and isomaltooligosaccharides. The initial transglucosylation by wild-type ANG in the presence of 100 mM maltose [Glc(α1-4)Glc] yields both α-(1→6)- and α-(1→4)-glucosidic linkages, the latter constituting ~25% of the total transfer reaction product. The maltotriose [Glc(α1-4)Glc(α1-4)Glc], α-(1→4)-glucosyl product disappears quickly, whereas the α-(1→6)-glucosyl products panose [Glc(α1-6)Glc(α1-4)Glc], isomaltose [Glc(α1-6)Glc], and isomaltotriose [Glc(α1-6)Glc(α1-6)Glc] accumulate. To modify the transglucosylation properties of ANG, residue Asn694, which was predicted to be involved in formation of the plus subsites of ANG, was replaced with Ala, Leu, Phe, and Trp. Except for N694A, the mutations enhanced the initial velocity of the α-(1→4)-transfer reaction to produce maltotriose, which was then degraded at a rate similar to that by wild-type ANG. With increasing reaction time, N694F and N694W mutations led to the accumulation of larger amounts of isomaltose and isomaltotriose than achieved with the wild-type enzyme. In the final stage of the reaction, the major product was panose (N694A and N694L) or isomaltose (N694F and N694W).

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP3371504	Isomaltotriose		3371-50-4	Price

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