Enzymatic synthesis of phenolic acid glucosyl esters to test activities on cholangiocarcinoma cells

While glycoside hydrolase family 1 (GH1) enzymes mostly catalyze hydrolysis reactions, rice Os9BGlu31 preferentially catalyzes transglycosylation to transfer a glucosyl moiety to another aglycone moiety to form a new glycosylated compound through a retaining mechanism. In this study, Os9BGlu31 was used to synthesize eight phenolic acid glucosyl esters, which were evaluated for activities in cholangiocarcinoma cells. The transglycosylation products of Os9BGlu31 wild type and its mutant variants were detected, produced on a milligram scale, and purified, and their structures were characterized by NMR spectroscopy. The transglycosylation products were evaluated by antioxidant and anti-proliferative assays, followed by an anti-migration assay for the selected phenolic acid glucosyl ester. Os9BGlu31 mutants produced higher yield and activity than wild-type enzymes on phenolic acids to produce phenolic acid glucosyl esters. Among these, gallic acid glucosyl ester (β-glucogallin) had the highest antioxidant activity and anti-proliferative activity in cholangiocarcinoma cells. It also inhibited the migration of cholangiocarcinoma cells. Our study demonstrated that rice Os9BGlu31 transglucosidase is a promising enzyme for glycosylation of bioactive compounds in one-step reactions and provides evidence that β-glucogallin inhibits cell proliferation and migration of cholangiocarcinoma cells. KEY POINTS: • Os9BGlu31 transglucosidases produced phenolic acid glucosyl esters for bioactivity testing. • Phenolic acid glucosyl esters were tested for cytotoxicity in cholangiocarcinoma cells. • β-Glucogallin displayed the highest inhibition of cholangiocarcinoma cell growth.

Slow digestion properties of long-sized isomaltooligosaccharides synthesized by a transglucosidase from Thermoanaerobacter thermocopriae

Isomaltooligosaccharides (IMOs) are widely used as prebiotic ingredients that promote colon health; however, recent studies revealed that these are slowly hydrolyzed to glucose within the small intestine. Here, novel α-glucans with a higher number of α-1,6 linkages were synthesized from maltodextrins using the Thermoanaerobacter thermocopriae-derived transglucosidase (TtTG) to decrease susceptibility to hydrolysis and improve slow digestion properties. The synthesized long-sized IMOs (l-IMOs; 70.1% of α-1,6 linkages), comprising 10-12 glucosyl units, exhibited slow hydrolysis to glucose when compared to commercial IMOs under treatment with mammalian α-glucosidase level. In male mice, the ingestion of l-IMOs significantly decreased the post-prandial glycemic response compared to other samples (p < 0.05). Therefore, enzymatically synthesized l-IMOs can be applied as functional ingredients for the modulation of blood glucose homeostasis in obesity, Type 2 diabetes, and other chronic diseases.

Structural, physicochemical and long-term retrogradation properties of wheat starch treated using transglucosidase

To reduce the wheat-flour-based food texture and flavor deterioration caused by starch retrogradation, herein wheat starch, the most ingredient in wheat flour, was modified by transglucosidase to delay long-term retrogradation of wheat starch. The study proposed promising data of transglucosidase-treated starch about structure, crystallinity and retrogradation kinetics. Structural properties showed that transglucosidase treatment shortened the average chain length from 19.49 to 16.10 and induced the dominance of amorphous state. Moreover, branching degree increased from 14.11% to 17.97% after transglucosidase treatment, resulting in higher water mobility. Amylose content increased from 25.33% to 59.00% due to the hydrolysis ability of transglucosidase. Relative crystallinity of the retrograded starches decreased from 24.33% to 14.50%. Furthermore, the Avrami parameters demonstrated that transglucosidase treatment significantly retarded the retrogradation rate of wheat starch due to the decrease of re-crystalline rate. The outcoming would supply a solid theory foundation for exploring the wheat staple foods with higher qualities.

Increasing the dietary fiber contents in isomaltooligosaccharides by dextransucrase reaction with sucrose as a glucosyl donor

Isomaltooligosaccharides (IMOs) have been widely used as alternative sweeteners owing to their stabilities, low calorigenic, and prebiotic properties. The aim of this research was to improve the functionality of conventionally produced IMOs by increasing dietary fiber (DF) content with newly synthesized α-(1,6)-linkages through the dextransucrase reaction. To optimize the reaction conditions, various combinations of IMO and sucrose concentrations were applied as acceptor and donor molecules, respectively. Soluble DF content in the enzymatically-modified IMOs increased significantly with the initial substrate mixture of 10 % sucrose and 20 % IMOs; both DF and IMO contents increased to 35 % and 54 %, respectively. It was clearly suggested a simple dextransucrase-involved bioprocess could be applied to increase the DF content to the IMOs produced via a conventional process without scarifying the original IMO contents. Thus, it will be expected that the DF-enhanced IMO products are potentially applicable as functional ingredients as sugar substitutes in the food industry.

Transglucosidase improves the bowel movements in type 2 diabetes mellitus patients: A preliminary randomized double-blind, placebo-controlled study

BACKGROUND

Recent studies have highlighted the relationship between gut microbiota and bowel movements.

OBJECTIVE

We aimed to evaluate transglucosidase treatment efficacy for bowel movements in patients with type 2 diabetes mellitus and to clarify the relationship between bowel movements, dietary habits, gut microbiota and fecal short-chain fatty acids.

METHODS

In this randomized double-blind, placebo-controlled study, 66 patients received placebo or transglucosidase (300 or 900 mg/day) orally, for 12 weeks. Fecal bacterial communities and short-chain fatty acids were analyzed before and after the treatment.

RESULTS

Transglucosidase treatment significantly (p < 0.05) affected fecal microbiota (Prevotella spp., Bacteroides spp., Bifidobacterium spp., and Clostridium subcluster XIVa) and fecal short-chain fatty acid (acetate, valerate, succinate and lactate) content. Clostridium cluster IV, Clostridium subcluster XIVa, Clostridium cluster XVIII and fecal pH increased significantly and order Lactobacillales decreased in patients with bowel movement disorder compared with controls. Transglucosidase treatment significantly improved bowel movements compared with placebo treatment (46.2%, 95% confidence interval: 19.2-74.9% vs. 0%, 95% confidence interval: 0-33.6%, p < 0.05). This effect was not observed in patients without bowel movement disorder.

CONCLUSION

Patients with bowel movement disorder suffer from gut dysbiosis. Transglucosidase treatment alleviates bowel movement disorder symptoms in type 2 diabetes mellitus patients by increasing fecal acetate level.

β-Glucosidases: Multitasking, moonlighting or simply misunderstood?

β-Glucosidases have a wide range of functions in plants, including roles in recycling of cell-wall oligosaccharides, defense, phytohormone signaling, secondary metabolism, and scent release, among others. It is not always clear which one is responsible for a specific function, as plants contain a large set of β-glucosidases. However, progress has been made in recent years in elucidating these functions. To help understand what is known and what remains ambiguous, we review the general approaches to investigating plant β-glucosidase functions. We consider information that has been gained regarding glycoside hydrolase family 1 enzyme functions utilizing these approaches in the past decade. In several cases, one enzyme has been assigned different biological functions by different research groups. We suggest that, at least in some cases, the ambiguity of an enzyme's function may come from having multiple functions that may help coordinate the response to injury or other stresses.

Pea starch (Pisum sativum L.) with slow digestion property produced using β-amylase and transglucosidase

Starches extracted from wrinkled (WP) and smooth (SP) peas were treated using β-amylase (B) alone and also with a combination of β-amylase and transglucosidase (BT). After enzymatic treatment, the proportions of slowly digested starch in WP-B, WP-BT, SP-B and SP-BT samples were increased by 6%, 9%, 9% and 12%, respectively. Starches treated by a combination of β-amylase and transglucosidase exhibited a smaller amount of longer amylopectin chains, a larger amount of short amylopectin chains, and higher branching fraction. The branching fraction was significantly increased, with an increase of 8%, 10%, 13% and 14% for WP-B, WP-BT, SP-B and SP-BT, respectively. The maximum absorbance and iodine binding of enzyme-treated starches were reduced compared with their native starch parents. The C-type crystalline structure completely disappeared after enzymatic treatment. The results support previous findings that increases in the amount of shorter amylopectin chains and branch fraction are likely to contribute to the slow digestion of starch.