Bacteria as source of diglycosidase activity: Actinoplanes missouriensis produces 6-O-α-l-rhamnosyl-β-d-glucosidase active on flavonoids

A novel diglycosidase for the transformation of naringin to naringenin and neohesperidose

A novel fungal diglycosidase that transforms naringin into naringenin and neohesperidose, a rare biotransformation, has been purified to homogeneity using a simple procedure involving precipitation of the enzyme from the culture filtrate of the fungal strain using 80 % saturation of ammonium sulphate, dissolving the precipitate in minimum volume of the buffer and dialysing that against the buffer. The purified enzyme gives single protein bands of molecular mass 64.6 kDa in SDS-PAGE analysis. The purity of the enzyme has been further confirmed by the appearance of single protein band in native page analysis. Using naringin as the substrate, the diglycosidase has Km and kcat values of 0.20 m mol L-1 and 0.66 s-1, respectively, at pH 4.0 and 313 K. The specific activity of the purified enzyme using naringin as the natural substrate is 1.018 katal/kg. The diglycosidase also transforms rutin into quercetin and rutinose but has no effect on hesperidin. The feasibilities of preparing neohesperidose from naringin and rutinose from rutin on milligram scales using the pure enzyme have been demonstrated. These results open the way for developing an enzymatic process for preparation of neohesperidose from naringin. The reported diglycosidase has immense future applications in food and pharmaceutical industries.

Phylogenomic analyses of the genus Actinoplanes: description of four novel genera

The genus Actinoplanes comprises 57 species (in February 2024) that are important components of ecosystems and are widely used in biotechnology, especially pharmaceuticals. Phylogenetic analysis of the family Micromonosporaceae (based on the 16S rRNA gene sequence) allowed us to group members of different genera into separate clades; however, the genus Actinoplanes was divided into three separate clades. Such phylogenetic heterogeneity could be due to the limitations of 16S rRNA gene analysis. In response to this heterogeneity, genomic phylogeny was performed. Phylogenomic reconstruction based on 324 single-copy orthologous genes allowed us to divide the genus Actinoplanes first into four clades and then, based on average nucleotide identity analysis, into five clades. Finally, chemotaxonomic analysis of each clade confirmed each clade's distinctiveness and the necessity to reclassify the genus Actinoplanes. The obtained data allowed us to divide the genus Actinoplanes into five genera: Actinoplanes, Paractinoplanes, Winogradskya, Symbioplanes and Amorphoplanes.

New insights of flavonoid glycosidases and their application in food industry

Flavonoids are significant natural nutraceuticals and a key component of dietary supplements. Given that flavonoid glycosides are more plentiful in nature and less beneficial to human health than their aglycone counterparts, they serve as potential precursors for flavonoid production. Glycosidases have shown substantial potential within the food industry, particularly in enhancing the organoleptic properties of juice, wine, and tea. When applied to food resources, glycosidases can amplify their biological activities, thereby improving the performance of functional foods. This review provides up-to-date information on flavonoid glycosidases, including their catalytic mechanisms, biochemical properties, and natural sources, as well as their applications within the food industry. The use of flavonoid glycosidases in improving food quality is also reviewed.

Rutinosidase and other diglycosidases: Rising stars in biotechnology

Diglycosidases are a special class of glycosidases (EC 3.2.1) that catalyze the separation of intact disaccharide moieties from the aglycone part. The main diglycosidase representatives comprise rutinosidases that cleave rutinose (α-l-Rha-(1-6)-β-d-Glc) from rutin or other rutinosides, and (iso)primeverosidases processing (iso)primeverosides (d-Xyl-(1-6)-β-d-Glc), but other activities are known. Notably, some diglycosidases may be ranked as monoglucosidases with enlarged substrate specificity. Diglycosidases are found in various microorganisms and plants. Diglycosidases are used in the food industry for aroma enhancement and flavor modification. Besides their hydrolytic activity, they also possess pronounced synthetic (transglycosylating) capabilities. Recently, they have been demonstrated to glycosylate various substrates in a high yield, including peculiar species like inorganic azide or carboxylic acids, which is a unique feature in biocatalysis. Rhamnose-containing compounds such as rutinose are currently receiving increased attention due to their proven activity in anti-cancer and dermatological experimental studies. This review demonstrates the vast and yet underrated biotechnological potential of diglycosidases from various sources (plant, microbial), and reveals perspectives on the use of these catalysts as well as of their products in biotechnology.

Flavonoids as Aglycones in Retaining Glycosidase-Catalyzed Reactions: Prospects for Green Chemistry

Flavonoids and their glycosides are abundant in many plant-based foods. The (de)glycosylation of flavonoids by retaining glycoside hydrolases has recently attracted much interest in basic and applied research, including the possibility of altering the glycosylation pattern of flavonoids. Research in this area is driven by significant differences in physicochemical, organoleptic, and bioactive properties between flavonoid aglycones and their glycosylated counterparts. While many flavonoid glycosides are present in nature at low levels, some occur in substantial quantities, making them readily available low-cost glycosyl donors for transglycosylations. Retaining glycosidases can be used to synthesize natural and novel glycosides, which serve as standards for bioactivity experiments and analyses, using flavonoid glycosides as glycosyl donors. Engineered glycosidases also prove valuable for the synthesis of flavonoid glycosides using chemically synthesized activated glycosyl donors. This review outlines the bioactivities of flavonoids and their glycosides and highlights the applications of retaining glycosidases in the context of flavonoid glycosides, acting as substrates, products, or glycosyl donors in deglycosylation or transglycosylation reactions.

Acuminosylation of Tyrosol by a Commercial Diglycosidase

A commercial glycosidase mixture obtained from Penicillium multicolor (Aromase H2) was found to comprise a specific diglycosidase activity, β-acuminosidase, alongside undetectable levels of β-apiosidase. The enzyme was tested in the transglycosylation of tyrosol using 4-nitrophenyl β-acuminoside as the diglycosyl donor. The reaction was not chemoselective, providing a mixture of Osmanthuside H and its counterpart regioisomer 4-(2-hydroxyethyl)phenyl β-acuminoside in 58% yield. Aromase H2 is therefore the first commercial β-acuminosidase which is also able to glycosylate phenolic acceptors.

Peculiarities and systematics of microbial diglycosidases, and their applications in food technology

Diglycosidases are endo-β-glucosidases that hydrolyze the heterosidic linkage of diglycoconjugates, thereby releasing in a single reaction the disaccharide and the aglycone. Plant diglycosidases belong to the glycoside hydrolase family 1 and are associated with defense mechanisms. Microbial diglycosidases exhibit higher diversity-they belong to the families 3, 5, and 55-and play a catabolic role. As diglycoconjugates are widespread in the environments, so are the microbial diglycosidases, which allow their utilization as nutritional source and carbon recycling. In the last 10 years, six microbial diglycosidases have been sequenced, and for two of them, the three-dimensional structure has been elucidated. This knowledge allowed the identification of their diverse phylogenetic origin, and gave insights into the understanding of the substrate specificity. Here, the last advances and the applications of microbial diglycosidases are reviewed. KEY POINTS: • Substrate specificity and phylogenetic relationships of diglycosidases are reviewed. • On-going and potential applications of diglycosidases are discussed.

Dual Substrate Specificity of the Rutinosidase from Aspergillus niger and the Role of Its Substrate Tunnel

Rutinosidases (α-l-rhamnopyranosyl-(1-6)-β-d-glucopyranosidases, EC 3.2.1.168, CAZy GH5) are diglycosidases that cleave the glycosidic bond between the disaccharide rutinose and the respective aglycone. Similar to many retaining glycosidases, rutinosidases can also transfer the rutinosyl moiety onto acceptors with a free -OH group (so-called transglycosylation). The recombinant rutinosidase from Aspergillus niger (AnRut) is selectively produced in Pichia pastoris. It can catalyze transglycosylation reactions as an unpurified preparation directly from cultivation. This enzyme exhibits catalytic activity towards two substrates; in addition to rutinosidase activity, it also exhibits β-d-glucopyranosidase activity. As a result, new compounds are formed by β-glucosylation or rutinosylation of acceptors such as alcohols or strong inorganic nucleophiles (NaN₃). Transglycosylation products with aliphatic aglycones are resistant towards cleavage by rutinosidase, therefore, their side hydrolysis does not occur, allowing higher transglycosylation yields. Fourteen compounds were synthesized by glucosylation or rutinosylation of selected acceptors. The products were isolated and structurally characterized. Interactions between the transglycosylation products and the recombinant AnRut were analyzed by molecular modeling. We revealed the role of a substrate tunnel in the structure of AnRut, which explained the unusual catalytic properties of this glycosidase and its specific transglycosylation potential. AnRut is attractive for biosynthetic applications, especially for the use of inexpensive substrates (rutin and isoquercitrin).

The flavonoid degrading fungus Acremonium sp. DSM 24697 produces two diglycosidases with different specificities

AbstractDiglycosidases hydrolyze the heterosidic linkage of diglycoconjugates, releasing the disaccharide and the aglycone. Usually, these enzymes do not hydrolyze or present only low activities towards monoglycosylated compounds. The flavonoid degrading fungus Acremonium sp. DSM 24697 produced two diglycosidases, which were termed 6-O-α-rhamnosyl-β-glucosidase I and II (αRβG I and II) because of their function of releasing the disaccharide rutinose (6-O-α-L-rhamnosyl-β-D-glucose) from the diglycoconjugates hesperidin or rutin. In this work, the genome of Acremonium sp. DSM 24697 was sequenced and assembled with a size of ~ 27 Mb. The genes encoding αRβG I and II were expressed in Pichia pastoris KM71 and the protein products were purified with apparent molecular masses of 42 and 82 kDa, respectively. A phylogenetic analysis showed that αRβG I grouped in glycoside hydrolase family 5, subfamily 23 (GH5), together with other fungal diglycosidases whose substrate specificities had been reported to be different from αRβG I. On the other hand, αRβG II grouped in glycoside hydrolase family 3 (GH3) and thus is the first GH3 member that hydrolyzes the heterosidic linkage of rutinosylated compounds. The substrate scopes of the enzymes were different: αRβG I showed exclusive specificity toward 7-O-β-rutinosyl flavonoids, whereas αRβG II hydrolyzed both 7-O-β-rutinosyl- and 3-O-β-rutinosyl- flavonoids. None of the enzymes displayed activity toward 7-O-β-neohesperidosyl- flavonoids. The recombinant enzymes also exhibited transglycosylation activities, transferring rutinose from hesperidin or rutin onto various alcoholic acceptors. The different substrate scopes of αRβG I and II may be part of an optimized strategy of the original microorganism to utilize different carbon sources.

"Sweet Flavonoids": Glycosidase-Catalyzed Modifications

Natural flavonoids, especially in their glycosylated forms, are the most abundant phenolic compounds found in plants, fruit, and vegetables. They exhibit a large variety of beneficial physiological effects, which makes them generally interesting in a broad spectrum of scientific areas. In this review, we focus on recent advances in the modifications of the glycosidic parts of various flavonoids employing glycosidases, covering both selective trimming of the sugar moieties and glycosylation of flavonoid aglycones by natural and mutant glycosidases. Glycosylation of flavonoids strongly enhances their water solubility and thus increases their bioavailability. Antioxidant and most biological activities are usually less pronounced in glycosides, but some specific bioactivities are enhanced. The presence of l-rhamnose (6-deoxy-α-l-mannopyranose) in rhamnosides, rutinosides (rutin, hesperidin) and neohesperidosides (naringin) plays an important role in properties of flavonoid glycosides, which can be considered as "pro-drugs". The natural hydrolytic activity of glycosidases is widely employed in biotechnological deglycosylation processes producing respective aglycones or partially deglycosylated flavonoids. Moreover, deglycosylation is quite commonly used in the food industry aiming at the improvement of sensoric properties of beverages such as debittering of citrus juices or enhancement of wine aromas. Therefore, natural and mutant glycosidases are excellent tools for modifications of flavonoid glycosides.

A novel Aspergillus oryzae diglycosidase that hydrolyzes 6-O-α-L-rhamnosyl-β-D-glucoside from flavonoids

α-L-Rhamnosyl-β-D-glucosidase (rutinosidase) hydrolyzes the glycosidic linkage between the disaccharide 6-O-α-L-rhamnosyl-β-D-glucoside (rutinose) and the aglycone. We identified a hypothetical protein (annotated as AO090012000917) encoded in the Aspergillus oryzae genome that exhibits sequence similarity with Aspergillus niger rutinosidase. The recombinant enzyme was expressed in Pichia pastoris GS115 and purified as a glyco-protein with apparent molecular mass of 65-75 kDa by SDS-PAGE. After N-deglycosylation, we observed a 42- and 40-kDa band, representing proteins before and after N-terminal signal peptide processing, respectively. Optimal enzymatic activity was observed at pH 4.0 and temperature of 45 °C. This enzyme is also significantly thermo-stable, with 90% activity retained after 1 h at 45 °C and 70% activity retained after 4 h, even at 50 °C. Biochemical characterization revealed that the enzyme has higher substrate specificity for 3-O-linked flavonoid β-rutinosides like rutin and kaempferol-3-O-rutinoside, than for 7-O-linked flavonoid β-rutinoside like hesperidin. However, no activity was found with naringin, diosmin, monoglycosylated chromogenic substrates, and polymeric laminarin substrate. Kinetic analyses showed that K _m value toward rutin was higher than those toward hesperidin and kaempferol-3-O-rutinoside. Meanwhile, k_cat value toward hesperidin was lower than those toward kaempferol-3-O-rutinoside and rutin. Overall, the catalytic efficiency (k_cat/K _m ) was highest for kaempferol-3-O-rutinoside.