Structural elements responsible for the glucosidic linkage‐selectivity of a glycoside hydrolase family 13 exo‐glucosidase

Abstract

Edited by Stuart FergusonKeywords: Dextran glucosidase a-GlucosidaseOligo-1,6-glucosidase Substrate specificity Glycoside hydrolase family 13 a b s t r a c t Glycoside hydrolase family 13 contains exo-glucosidases specific for a-(1 ? 4)-and a-(1 ? 6)-linkages including a-glucosidase, oligo-1,6-glucosidase, and dextran glucosidase. The a-(1 ? 6)-linkage selectivity of Streptococcus mutans dextran glucosidase was altered to a-(1 ? 4)-linkage selectivity through site-directed mutations at Val195, Lys275, and Glu371. V195A showed 1300-fold higher k cat /K m for maltose than wild-type, but its k cat /K m for isomaltose remained 2-fold higher than for maltose. K275A and E371A combined with V195A mutation only decreased isomaltase activity. V195A/K275A, V195A/E371A, and V195A/K275A/E371A showed 27-, 26-, and 73-fold higher k cat /K m for maltose than for isomaltose, respectively. Consequently, the three residues are structural elements for recognition of the a-(1 ? 6)-glucosidic linkage.

Function and structure of GH13_31 α‐glucosidase with high α‐(1→4)‐glucosidic linkage specificity and transglucosylation activity

“…). Although its product is recorded as oligo‐1,6‐glucosidase in GenBank, it possesses an Ala next to the catalytic nucleophile as frequently observed in α‐(1→4)‐glucoside‐acting AGase without carrying three residues essential for α‐(1→6)‐linkage specificity . Thus, it was predicted to be α‐(1→4)‐specific AGase, and the corresponding gene in Bacillus sp.…”

“…α‐(1→4)‐Linkage‐specific GH13 AGases have Ala or Thr at this position (Fig. ), and this Ala/Thr is thought to be important for linkage specificity as demonstrated in Streptococcus mutans dextran glucosidase ( Sm DG) . In Bsp GH13_31A, His203 and Asn258, located on the β→α loops 4 and 5, respectively, were regarded to be involved in forming subsite +1 through hydrogen bonding with 2‐O of the d ‐glucosyl residue (Fig.…”

“…SAM1606, Gly273 at this position is important for activity toward trehalose [39]. In a-(1?6)-linkage-specific exo-acting enzymes (oligo-1,6-glucosidase and dextran glucosidase), hydrogen bonds in subsite +1, provided by Lys on the b?a loop 6 and Glu on the second a-helix in domain B 0 , are important for activity toward isomaltooligosaccharides [29]. In BspAG13_31A, the b?a loop 6 was disordered in the substrate complexes (indicating no apparent interaction with substrates), and Gly384 is situated at the position of the Glu in domain B 0 .…”

Escherichia coli expression and characterization of α-amylase from Geobacillus thermodenitrificans DSM-465

“…Amylase are essential enzyme used in carbohydrate metabolism by the hydrolysis of glycosidic bonds. This enzyme is widely distributed in natural world (Saburi et al, 2015) such as in plant, animals, fungi and bacteria (Ribeiro et al, 2000;Hagihara et al, 2001). Amylase have a lot of industrial applications (Bassinello et al, 2002) including starch and its derivative industries like, detergent, textile, bakery, fermentation, paper making, ethanol production, food and brewing industry (Schroder et al, 2015).…”

Evaluation and directed evolution for thermostability improvement of a GH 13 thermostable α-glucosidase from Thermus thermophilus TC11

“…Glycoside hydrolases (GHs), catalyzing the hydrolysis of glycosidic linkages, are widely distributed in the natural world, and play essential roles in the carbohydrate metabolism [ 1 ]. In the CAZy database, GHs are classified into 133 families based on sequence similarity ( http://www.cazy.org ) [ 2 ].…”