3 research outputs found
Transglycosylation Properties of a Novel α-1,4-Glucanotransferase from Bacteroides thetaiotaomicron and Its Application in Developing an α-Glucosidase-Specific Inhibitor
In this study, α-glucanotransferase from Bacteroides thetaiotaomicron was expressed in Escherichia coli and characterized. Conserved amino-acid sequence alignment showed that Bacteroides thetaiotaomicron α-glucanotransferase (BtαGTase) belongs to the glycoside hydrolase family 77. The enzyme exhibited optimal catalytic activity at 60°C and pH 3.0. BtαGTase catalyzed transglycosylation reactions that produced only glycosyl or maltosyl transfer products, which are preferable for the generation of transglycosylated products with high yield. The 1-deoxynojirimycin (DNJ) glycosylation product G1-DNJ was generated using BtαGTase, and the inhibitory effect of G1-DNJ was analyzed. A kinetic study of inhibition revealed that G1-DNJ inhibited α-glucosidase to a greater extent than did DNJ but did not show any inhibitory effects towards α-amylase, suggesting that G1-DNJ is a potential candidate for the prevention of diabetes
Characterization of a Novel Maltose-Forming α‑Amylase from Lactobacillus plantarum subsp. <i>plantarum</i> ST-III
A novel maltose (G2)-forming α-amylase
from Lactobacillus plantarum subsp. <i>plantarum</i> ST-III was expressed in Escherichia
coli and characterized. Analysis of conserved amino
acid sequence alignments
showed that L. plantarum maltose-producing
α-amylase (LpMA) belongs to glycoside hydrolase family 13. The
recombinant enzyme (LpMA) was a novel G2-producing α-amylase.
The properties of purified LpMA were investigated following enzyme
purification. LpMA exhibited optimal activity at 30 °C and pH
3.0. It produced only G2 from the hydrolysis of various substrates,
including maltotriose (G3), maltopentaose (G5), maltosyl β-cyclodextrin
(G2-β-CD), amylose, amylopectin, and starch. However, LpMA was
unable to hydrolyze cyclodextrins. Reaction pattern analysis using
4-nitrophenyl-α-d-maltopentaoside (<i>p</i>NPG5) demonstrated that LpMA hydrolyzed <i>p</i>NPG5 from
the nonreducing end, indicating that LpMA is an exotype α-amylase.
Kinetic analysis revealed that LpMA had the highest catalytic efficiency
(<i>k</i><sub>cat</sub>/<i>K</i><sub>m</sub> ratio)
toward G2-β-CD. Compared with β-amylase, a well-known
G2-producing enzyme, LpMA produced G2 more efficiently from liquefied
corn starch due to its ability to hydrolyze G3