Dataset Information

Structure-function relationships of family GH70 glucansucrase and 4,6-?-glucanotransferase enzymes, and their evolutionary relationships with family GH13 enzymes.

ABSTRACT: Lactic acid bacteria (LAB) are known to produce large amounts of ?-glucan exopolysaccharides. Family GH70 glucansucrase (GS) enzymes catalyze the synthesis of these ?-glucans from sucrose. The elucidation of the crystal structures of representative GS enzymes has advanced our understanding of their reaction mechanism, especially structural features determining their linkage specificity. In addition, with the increase of genome sequencing, more and more GS enzymes are identified and characterized. Together, such knowledge may promote the synthesis of ?-glucans with desired structures and properties from sucrose. In the meantime, two new GH70 subfamilies (GTFB- and GTFC-like) have been identified as 4,6-?-glucanotransferases (4,6-?-GTs) that represent novel evolutionary intermediates between the family GH13 and "classical GH70 enzymes". These enzymes are not active on sucrose; instead, they use (?1 ? 4) glucans (i.e. malto-oligosaccharides and starch) as substrates to synthesize novel ?-glucans by introducing linear chains of (?1 ? 6) linkages. All these GH70 enzymes are very interesting biocatalysts and hold strong potential for applications in the food, medicine and cosmetic industries. In this review, we summarize the microbiological distribution and the structure-function relationships of family GH70 enzymes, introduce the two newly identified GH70 subfamilies, and discuss evolutionary relationships between family GH70 and GH13 enzymes.

SUBMITTER: Meng X

PROVIDER: S-EPMC4919382 | biostudies-literature | 2016 Jul

REPOSITORIES: biostudies-literature

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Structure-function relationships of family GH70 glucansucrase and 4,6-α-glucanotransferase enzymes, and their evolutionary relationships with family GH13 enzymes.

Meng Xiangfeng X Gangoiti Joana J Bai Yuxiang Y Pijning Tjaard T Van Leeuwen Sander S SS Dijkhuizen Lubbert L

Cellular and molecular life sciences : CMLS 20160507 14

Lactic acid bacteria (LAB) are known to produce large amounts of α-glucan exopolysaccharides. Family GH70 glucansucrase (GS) enzymes catalyze the synthesis of these α-glucans from sucrose. The elucidation of the crystal structures of representative GS enzymes has advanced our understanding of their reaction mechanism, especially structural features determining their linkage specificity. In addition, with the increase of genome sequencing, more and more GS enzymes are identified and characterized ...[more]

PMID: 27155661

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Project description:Glucansucrases (GSs) in glycoside hydrolase family 70 (GH70) catalyze the synthesis of ?-glucans from sucrose, a reaction that is widely seen in lactic acid bacteria (LAB). These enzymes have been implicated in many aspects of microbial life. Products of GSs have great commercial value as food supplements and medical materials; therefore, these enzymes have attracted much attention from both science and industry. Certain issues concerning the origin and evolution of GSs are still to be addressed, although an increasing number of GH70 enzymes have been characterized. This study describes a GS enzyme with the appearance of a branching sucrase (BrS). Structural analysis indicated that this GS enzyme produced a type of glucan composed of an ?-(1?6) glucosidic backbone and ?-(1?4) branches, as well as a considerable amount of ?-(1?3) branches, distinguishing it from the GSs identified so far. Moreover, sequence-based analysis of the catalytic core of this enzyme suggested that it might be an evolutionary intermediate between the BrS and GS subgroups. These results provide an evolutionary link between these subgroups of GH70 enzymes and shed new light on the origination of GSs.IMPORTANCE GH70 GSs catalyze the synthesis of ?-glucans from sucrose, a reaction that is widely seen in LAB. Products of these enzymes have great commercial value as food supplements and medical materials. Moreover, these enzymes have attracted much attention from scientists because they have potential in tailored synthesis of ?-glucans with desired structures and properties. Although more and more GSs have been characterized, the origin and evolution of these enzymes have not been well addressed. This study describes a GS with the appearance of a BrS (i.e., high levels of similarity to BrSs in sequence analysis). Further analysis indicated that this enzyme synthesized a type of insoluble glucan composed of an ?-(1?6) glucosidic backbone and many ?-(1?4)- and ?-(1?3)-linked branches, the linkage composition of which has rarely been reported in the literature. This BrS-like GS enzyme might be an evolutionary intermediate between BrS and GS enzymes.

Project description:Previously, we have identified and characterized 4,6-?-glucanotransferase enzymes of the glycosyl hydrolase (GH) family 70 (GH70) that cleave (?1?4)-linkages in amylose and introduce (?1?6)-linkages in linear chains. The 4,6-?-glucanotransferase of Lactobacillus reuteri 121, for instance, converts amylose into an isomalto/malto-polysaccharide (IMMP) with 90% (?1?6)-linkages. Over the years, also, branching sucrase enzymes belonging to GH70 have been characterized. These enzymes use sucrose as a donor substrate to glucosylate dextran as an acceptor substrate, introducing single -(1?2,6)-?-d-Glcp-(1?6)- (Leuconostoc citreum enzyme) or -(1?3,6)-?-d-Glcp-(1?6)-branches (Leuconostoc citreum, Leuconostoc fallax, Lactobacillus kunkeei enzymes). In this work, we observed that the catalytic domain 2 of the L. kunkeei branching sucrase used not only dextran but also IMMP as the acceptor substrate, introducing -(1?3,6)-?-d-Glcp-(1?6)-branches. The products obtained have been structurally characterized in detail, revealing the addition of single (?1?3)-linked glucose units to IMMP (resulting in a comb-like structure). The in vitro digestibility of the various ?-glucans was estimated with the glucose generation rate (GGR) assay that uses rat intestinal acetone powder to simulate the digestive enzymes in the upper intestine. Raw wheat starch is known to be a slowly digestible carbohydrate in mammals and was used as a benchmark control. Compared to raw wheat starch, IMMP and dextran showed reduced digestibility, with partially digestible and indigestible portions. Interestingly, the digestibility of the branching sucrase modified IMMP and dextran products considerably decreased with increasing percentages of (?1?3)-linkages present. The treatment of amylose with 4,6-?-glucanotransferase and branching sucrase/sucrose thus allowed for the synthesis of amylose/starch derived ?-glucans with markedly reduced digestibility. These starch derived ?-glucans may find applications in the food industry.

Dataset Information

Structure-function relationships of family GH70 glucansucrase and 4,6-?-glucanotransferase enzymes, and their evolutionary relationships with family GH13 enzymes.

Publications

Structure-function relationships of family GH70 glucansucrase and 4,6-α-glucanotransferase enzymes, and their evolutionary relationships with family GH13 enzymes.

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