Enzyme and microbial technology for synthesis of bioactive oligosaccharides: an update

Abstract

Oligosaccharides, in either free or bound forms, play crucial roles in a wide range of biological processes. Increasing appreciation of their roles in cellular communication, interaction, pathogenesis, and prebiotic functions has stimulated tremendous interests in their synthesis. Pure and structurally defined oligosaccharides are essential for fundamental studies. On the other hand, for those with near term medical and nutraceutical applications, their large-scale synthesis is necessary. Unfortunately, oligosaccharides are notoriously difficult in their synthesis, and their enormous diverse structures leave a vast gap between what have been synthesized in laboratory and those present in various biological systems. While enzymes and microbes are nature's catalysts for oligosaccharides, their effective use is not without challenges. Using examples of galactose-containing oligosaccharides, this review analyzes the pros and cons of these two forms of biocatalysts and provides an updated view on the status of biocatalysis in this important field. Over the past few years, a large number of novel galactosidases were discovered and/or engineered for improved synthesis via transglycosylation. The use of salvage pathway for regeneration of uridine diphosphate (UDP)-galactose has made the use of Leloir glycosyltransferases simpler and more efficient. The recent success of large-scale synthesis of 2' fucosyllactose heralded the power of whole-cell biocatalysis as a scalable technology. While it still lags behind enzyme catalysis in terms of the number of oligosaccharides synthesized, an acceleration in the use of this form of biocatalyst is expected as rapid advances in synthetic biology have made the engineering of whole cell biocatalysts less arduous and less time consuming.

Harnessing glycoenzyme engineering for synthesis of bioactive oligosaccharides

“…The generated enzyme libraries (approx. 10 3 -10 9 variants) require then a suitable high-throughput screening method such as cell-surface display or cell-free systems [29,30] [9,57] and they have been advantageously used, often in combination with a chemically prepared oligosaccharide precursor, for the synthesis of glycans [58][59][60][61].…”

“…The field is rapidly evolving with the democratization of these technologies, which could also royalsocietypublishing.org/journal/rsfs Interface Focus 9: 20180069 be combined with post-synthesis and specific chemical labelling of the reaction products to facilitate product analysis at high throughput. In parallel, cell development for specific carbohydrate production inspired from existing biosynthetic pathways is also rapidly progressing [9,158]. The incorporation of engineered enzymes gives total freedom to even more creative pathways to produce in vivo bioactive oligosaccharides and glycoconjugates at large scale and offers exciting perspectives.…”

Decoupling of recombinant protein production from Escherichia coli cell growth enhances functional expression of plant Leloir glycosyltransferases

“…The enzymes also referred to collectively as Leloir GTs, transfer glycosyl residues from sugar nucleotide donors to specific positions on acceptor substrates (Liang et al, 2015). Compared with other enzymes (e.g., glycoside hydrolases; glycoside phosphorylases) that are also able to glycosylate small molecules, the GTs often present a unique combination of high chemo/regioselectivity and relatively flexible substrate specificity (R. Chen, 2018;Desmet et al, 2012;Thuan & Sohng, 2013). The plant GTs are, therefore, promising catalysts for glycoside production (for reviews, see: Lim, 2005;Nidetzky, Gutmann, & Zhong, 2018).…”

Structural Features of Sulfated Glucuronomannan Oligosaccharides and Their Antioxidant Activity

“…Oligosaccharides play crucial roles in a wide range of biological processes, such as cellular communication, pathogenesis and prebiotic functions [ 1 , 2 , 3 , 4 , 5 ]. For this reason, they are also being developed for new drugs.…”