Hiromi Nishiura

Glucosylation of Acetic Acid by Sucrose Phosphorylase

Transglucosylation from sucrose to acetic acid by sucrose phosphorylase (EC 2.4.1.7) was studied. 1-O-Acetyl-α-D-glucopyranose was isolated as the main product of the enzyme reaction. We also compared the pH-dependence of transglycosylation catalyzed by sucrose phosphorylase toward carboxyl and hydroxyl groups. With hydroquinone as an acceptor molecule, the transfer ratio of glucose residue was higher at neutral pH. This pH-activity profile was similar to that of the phosphorolysis of sucrose by sucrose phosphorylase, but with acetic acid as an acceptor molecule, the transfer ratio of glucose residue was higher at low pH. These findings suggest that the undissociated carboxyl group is essential to the acceptor molecule for the transglycosylation reaction of sucrose phosphorylase. In a sensory test, the sour taste of acetic acid was markedly reduced by glucosylation. The threshold value of the sour taste of acetic acid glucosides was approximately 100 times greater than that of acetic acid.

A Novel Nano-Capsule of ñ-Lipoic Acid as a Template of Core-Shell Structure Constructed by Self-Assembly

Mast cells (MC) and peripheral blood basophils (PBB) are well known for their role in the allergic response mediated through high affinity IgE receptors (FceRI). However, these cells can also be stimulated by other non-allergic secretagogues to release their inflammatory mediators. Certain fullerene derivatives (FD) have already been shown to stabilize FceRI-mediated MC/PBB responses, but it is not know if they also stabilize these cells through non-IgEmediated mechanisms. A panel of FD was synthesized and tested for their ability to inhibit non-FceRI mediated release from human MC and PBB. It was found that specifically engineered FD could significantly inhibit calcium ionophore, compound 48/80, somatostatin, and poly L-lysine induced MC degranulation and cytokine production, as well as blunt degranulation and cytokine production from N-formyl-methionine-leucine-phenylalanine (fMLP), poly L-lysine, and calcium ionophore stimulated PBB. The mechanism of inhibition was due in part to the prevention of secretagogueinduced increases in cellular reactive oxygen species (ROS) and calcium levels as well as the reduced activation of the MAPK signaling intermediates ERK1/ERK2 and LAT. Additionally, preincubation of MC with FD blunted the prostaglandin D2 (PGD2) production upon exposure to inflammatory stimuli. In both cell types, the extent of inhibition of mediator release in response to each secretagogue was dependent on the moieties/side chains attached to the carbon cage. These results further extend the utility of fullerene nanomaterials to control mediator release through non-IgE mediated pathways in MC/PBB.

Sucrose phosphorylases catalyze transglycosylation reactions on carboxylic acid compounds

Two sucrose phosphorylases were employed for glycosylation of carboxylic acid compounds. Streptococcus mutans sucrose phosphorylase showed remarkable transglycosylating activity, especially under acidic conditions. Leuconostoc mesenteroides sucrose phosphorylase exhibited very weak transglycosylating activity. Three main products were detected from the reaction mixture using benzoic acid and sucrose as an acceptor and a donor molecule, respectively. These compounds were identified as 1-O-benzoyl α-d-glucopyranoside, 2-O-benzoyl α-d-glucopyranose, and 2-O-benzoyl β-d-glucopyranose by 1D-and 2D-NMR analyses of the isolated products and their acetylated products. Time-course analyses proved that 1-O-benzoyl α-d-glucopyranoside was initially produced by the transglycosylation reaction of the enzyme. 2-O-Benzoyl α-d-glucopyranose and 2-O-benzoyl β-d-glucopyranose were produced from 1-O-benzoyl α-d-glucopyranoside by intramolecular acyl migration reaction. S. mutans sucrose phosphorylase showed broad acceptor-specificity. This sucrose phosphorylase catalyzed transglycosylation to various carboxylic compounds such as short-chain fatty acids, hydroxy acids, dicarboxylic acids, and phenolic carboxylic acids. 1-O-Acetyl α-d-glucopyranoside was also enzymatically synthesized by transglucosylation reaction of the enzyme. The sensory test of acetic acid and the glucosides revealed that the sour taste of acetic acid glucosides was significantly lower than that of acetic acid.

Glycosylation of Carboxylic Group: A new Reaction of Sucrose Phosphorylases

Abstract We found a new reaction of sucrose phosphorylases; transglycosylation of carboxyl group. Sucrose phosphorylases from two different sources were tested for glycosylation of carboxylic acid compounds. Streptococcus mutans sucrose phosphorylase showed remarkable transglycosylating activity, especially under acidic conditions. Leuconostoc mesenteroides sucrose phosphorylase exhibited very weak transglycosylating activity. When benzoic acid and sucrose were used as an acceptor and a donor molecule, 1-O- benzoyl α-D-glucopyranoside was produced which was identified by 1D- and 2D-NMR analyses of the purified product and its acetylated product. S. mutans sucrose phosphorylase showed broad acceptor-specificity. The sucrose phosphorylase catalyzed transglycosylation to various carboxylic compounds such as short-chain fatty acids, hydroxy acids, dicarboxylic acids, phenolic carboxylic acids, and acetic acid.