Glycosylation of Epigallocatechin Gallate by Engineered Glycoside Hydrolases from Talaromyces amestolkiae: Potential Antiproliferative and Neuroprotective Effect of These Molecules

Abstract

Glycoside hydrolases (GHs) are enzymes that hydrolyze glycosidic bonds, but some of them can also catalyze the synthesis of glycosides by transglycosylation. However, the yields of this reaction are generally low since the glycosides formed end up being hydrolyzed by these same enzymes. For this reason, mutagenic variants with null or drastically reduced hydrolytic activity have been developed, thus enhancing their synthetic ability. Two mutagenic variants, a glycosynthase engineered from a β-glucosidase (BGL-1-E521G) and a thioglycoligase from a β-xylosidase (BxTW1-E495A), both from the ascomycete Talaromyces amestolkiae, were used to synthesize three novel epigallocatechin gallate (EGCG) glycosides. EGCG is a phenolic compound from green tea known for its antioxidant effects and therapeutic benefits, whose glycosylation could increase its bioavailability and improve its bioactive properties. The glycosynthase BGL-1-E521G produced a β-glucoside and a β-sophoroside of EGCG, while the thioglycoligase BxTW1-E495A formed the β-xyloside of EGCG. Glycosylation occurred in the 5″ and 4″ positions of EGCG, respectively. In this work, the reaction conditions for glycosides’ production were optimized, achieving around 90% conversion of EGCG with BGL-1-E521G and 60% with BxTW1-E495A. The glycosylation of EGCG caused a slight loss of its antioxidant capacity but notably increased its solubility (between 23 and 44 times) and, in the case of glucoside, also improved its thermal stability. All three glycosides showed better antiproliferative properties on breast adenocarcinoma cell line MDA-MB-231 than EGCG, and the glucosylated and sophorylated derivatives induced higher neuroprotection, increasing the viability of SH-S5Y5 neurons exposed to okadaic acid.

The glycoside hydrolase gene family profile and microbial function of Debaryomyces hansenii Y4 during South-road dark tea fermentation

“…In view of the apparent decrease in the levels of EC, EGCG and so forth after fermentation and the relationship between catechin monomers and GH genes, it cannot be excluded that the expression of some GH genes probably leads to an obvious decrease in the levels of specific catechin monomers by mediating the glycosylation of catechins, as researchers have discovered that certain GHs can catalyze transglycosylation reactions, e.g., transferring a sugar unit to a nucleophilic acceptor other than water under certain conditions ( Prieto et al, 2021 ; Wang et al, 2022 ). Cho et al (2011) have employed amylosucrase from Deinococcus geothermalis DSM 11300 to biosynthesize (+)-catechin glycosides via linking glucose or maltose molecule to (+)-catechin, and Méndez-Líter et al (2022) also successfully synthesized 3 novel EGCG-glycosides utilizing engineered transformed β-glucosidase and β-xylosidase from Talaromyces amestolkiae. The production of glycosylated catechin will result in an evident reduction in the levels of some unique catechin monomers.…”

Bioavailability and Bioactivity of Plant Antioxidants

“…Increasing the bioavailability and improving the bioactive properties of compounds known for their antioxidant activity and therapeutic benefits can be achieved by subjecting them to a glycosylation reaction. The research of Méndez-Líter’s team concerned the optimization of the production of three new epigallocatechin gallate (EGCG) glycosides (glucoside, sophorose, xyloside) by transglycosylation using two engineered glycoside hydrolases from the fungus Talaromyces amestolkiae [ 12 ]. The obtained derivatives differed in solubility (glucoside > xyloside > sophoroside) and thermal stability.…”

“…The obtained derivatives differed in solubility (glucoside > xyloside > sophoroside) and thermal stability. In addition, glycosylation resulted in the improved bioactive properties of the derivatives compared to EGCG, manifested by better antiproliferative properties on breast adenocarcinoma cell line MDA-MB-231 than EGCG, and the glucosylated and sophorylated derivatives induced higher neuroprotection, increasing the viability of SH-S5Y5 neurons exposed to okadaic acid [ 12 ].…”