Strategies for modulating transglycosylation activity, substrate specificity, and product polymerization degree of engineered transglycosylases

Glycosides are widely used in many fields due to their favorable biological activity. The traditional plant extractions and chemical methods for glycosides production are limited by environmentally unfriendly, laborious protecting group strategies and low yields. Alternatively, enzymatic glycosylation has drawn special attention due to its mild reaction conditions, high catalytic efficiency, and specific stereo-/regioselectivity. Glycosyltransferases (GTs) and retaining glycoside hydrolases (rGHs) are two major enzymes for the formation of glycosidic linkages. Therein GTs generally use nucleotide phosphate activated donors. In contrast, GHs can use broader simple and affordable glycosyl donors, showing great potential in industrial applications. However, most rGHs mainly show hydrolysis activity and only a few rGHs, namely non-Leloir transglycosylases (TGs), innately present strong transglycosylation activities. To address this problem, various strategies have recently been developed to successfully tailor rGHs to alleviate their hydrolysis activity and obtain the engineered TGs. This review summarizes the current modification strategies in TGs engineering, with a special focus on transglycosylation activity enhancement, substrate specificity modulation, and product polymerization degree distribution, which provides a reference for exploiting the transglycosylation potentials of rGHs.

Reprint of: Advanced glycosidases as ingenious biosynthetic instruments

Until recently, glycosidases, naturally hydrolyzing carbohydrate-active enzymes, have found few synthetic applications in industry, being primarily used for cleaving unwanted carbohydrates. With the establishment of glycosynthase and transglycosidase technology by genetic engineering, the view of glycosidases as industrial biotechnology tools has started to change. Their easy production, affordability, robustness, and substrate versatility, added to the possibility of controlling undesired side hydrolysis by enzyme engineering, have made glycosidases competitive synthetic tools. Current promising applications of engineered glycosidases include the production of well-defined chitooligomers, precious galactooligosaccharides or specialty chemicals such as glycosylated flavonoids. Other synthetic pathways leading to human milk oligosaccharides or remodeled antibodies are on the horizon. This work provides an overview of the synthetic achievements to date for glycosidases, emphasizing the latest trends and outlining possible developments in the field.

Advanced glycosidases as ingenious biosynthetic instruments

Until recently, glycosidases, naturally hydrolyzing carbohydrate-active enzymes, have found few synthetic applications in industry, being primarily used for cleaving unwanted carbohydrates. With the establishment of glycosynthase and transglycosidase technology by genetic engineering, the view of glycosidases as industrial biotechnology tools has started to change. Their easy production, affordability, robustness, and substrate versatility, added to the possibility of controlling undesired side hydrolysis by enzyme engineering, have made glycosidases competitive synthetic tools. Current promising applications of engineered glycosidases include the production of well-defined chitooligomers, precious galactooligosaccharides or specialty chemicals such as glycosylated flavonoids. Other synthetic pathways leading to human milk oligosaccharides or remodeled antibodies are on the horizon. This work provides an overview of the synthetic achievements to date for glycosidases, emphasizing the latest trends and outlining possible developments in the field.

Characterization of a high-affinity sialic acid-specific CBM40 from Clostridium perfringens and engineering of a divalent form

CBMs (carbohydrate-binding modules) are a class of polypeptides usually associated with carbohydrate-active enzymatic sites. We have characterized a new member of the CBM40 family, coded from a section of the gene NanI from Clostridium perfringens. Glycan arrays revealed its preference towards α(2,3)-linked sialosides, which was confirmed and quantified by calorimetric studies. The CBM40 binds to α(2,3)-sialyl-lactose with a Kd of ∼30 μM, the highest affinity value for this class of proteins. Inspired by lectins' structure and their arrangement as multimeric proteins, we have engineered a dimeric form of the CBM, and using SPR (surface plasmon resonance) we have observed 6–11-fold binding increases due to the avidity affect. The structures of the CBM, resolved by X-ray crystallography, in complex with α(2,3)- or α(2,6)-sialyl-lactose explain its binding specificity and unusually strong binding.