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Koo, Ye-Seul,Ko, Dam-Seul,Jeong, Da-Woon,Shim, Jae-Hoon American Chemical Society 2017 Journal of agricultural and food chemistry Vol.65 No.11
<P>Cyclodextrins (CDs) are produced from starch by cyclodextrin glucanotransferase (CGTase), which has cyclization activity. Specifically, alpha-CD is an important biomolecule, as it is a molecular carrier and soluble dietary fiber used in the food industry. Upon inspection of the conserved regions of the glycoside hydrolase (GH) 13 family amylases, the amino acids K232 and H233 of CGTase were identified as playing an important role in enzyme reaction specificity. A novel CD hydrolyzing enzyme, cyclodextrin glycosyl transferase.(CGTase)-alpha, was developed using site-directed mutagenesis at these positions. Action pattern analysis using various substrates revealed that CGTase-alpha was able to hydrolyze beta- and gamma-CD, but not alpha-CD. This selective CD hydrolyzing property was employed to purify a alpha-CD from alpha-CD mixture solution. The alpha-CD that remained after treatment with CGTase-alpha and exotype glucoamylase was purified using hydrophobic interaction chromatography with 99% purity.</P>
Choi, Hye-Jeong,Ko, Dam-Seul,Kim, Na-Ri,Choung, Woo-Jae,Koo, Ye-Seul,Jeong, Da-Woon,Shim, Jae-Hoon Hindawi Limited 2018 Journal of chemistry Vol.2018 No.-
<P>In this study, <I>α</I>-glucanotransferase from <I>Bacteroides thetaiotaomicron</I> was expressed in <I>Escherichia coli</I> and characterized. Conserved amino-acid sequence alignment showed that <I>Bacteroides thetaiotaomicron α</I>-glucanotransferase (Bt<I>α</I>GTase) belongs to the glycoside hydrolase family 77. The enzyme exhibited optimal catalytic activity at 60°C and pH 3.0. Bt<I>α</I>GTase 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 Bt<I>α</I>GTase, and the inhibitory effect of G1-DNJ was analyzed. A kinetic study of inhibition revealed that G1-DNJ inhibited <I>α</I>-glucosidase to a greater extent than did DNJ but did not show any inhibitory effects towards <I>α</I>-amylase, suggesting that G1-DNJ is a potential candidate for the prevention of diabetes.</P>
Choung, Woo-Jae,Hwang, Seung Hwan,Ko, Dam-Seul,Kim, Set Byeol,Kim, Seo Hyun,Jeon, Sung Ho,Choi, Hee-Don,Lim, Soon Sung,Shim, Jae-Hoon American Chemical Society 2017 Journal of agricultural and food chemistry Vol.65 No.13
<P>Kaempferol-3-O-beta-D-glucopyranoside (astragalin, AS), a major flavonoid that exists in various plants, exerts antioxidant, antitumor, anti-human immunodeficiency virus (HIV), and anti-inflammatory effects. However, the low water solubility of AS limits its use. In this study, we used cyclodextrin glucanotransferase (CGTase) with maltose (G2) as a donor molecule to enzymatically modify AS to improve its water solubility and physiochemical properties. We isolated the glycosylated astragalin (G1-AS) and identified the structure of G1-AS as kaempferol-3-O-beta-D-glucop-yranosyl-(1 -> 4)-O-alpha-D-glucopyranoside, where one glucose residue was transferred to AS. Gl-AS retained the antioxidative activity of the original AS compound; however, the solubility of G1-AS was 65-fold higher than that of AS. In addition, GI-AS showed enhanced anti-inflammatory effects and aldose reductase inhibitory activity compared to AS when applied to rat lenses.</P>
Jeon, Hye-Yeon,Kim, Na-Ri,Lee, Hye-Won,Choi, Hye-Jeong,Choung, Woo-Jae,Koo, Ye-Seul,Ko, Dam-Seul,Shim, Jae-Hoon American Chemical Society 2016 Journal of agricultural and food chemistry Vol.64 No.11
<P>A novel maltose (G2)-forming alpha-amylase from Lactobacillus plantarum subsp. plantarum ST-III was expressed in Escherichia coli and characterized. Analysis of conserved amino acid sequence alignments showed that L. plantarum maltose producing alpha-amylase (LpMA) belongs to glycoside hydrolase family 13. The recombinant enzyme (LpMA) was a novel G2 producing alpha-amylase. The properties of.purified LpMA were investigated following enzyme purification. LpMA exhibited optimal activity at 30 degrees C and pH 3.0. It produced only G2 from the hydrolysis of various substrates, including maltotriose (G3), maltopentaose (GS), maltosyl beta-cyclodextrin (G2-beta-CD), amylose, amylopectin, and starch. However, LpMA was unable to hydrolyze cyclodextrins. Reaction pattern analysis using 4-nitrophenyl-alpha-D-maltopentaoside (pNPGS) demonstrated that LpMA hydrolyzed pNPGS from the nonreducing end, indicating that LpMA is an exotype alpha-amylase. Kinetic analysis revealed that LpMA had the highest catalytic efficiency (k(cat)/K-m ratio) toward G2-beta-CD. Compared with beta-amylase, a well-known G2-producing enzyme, LpMA produced G2 more efficiently from liquefied corn starch due to its ability to hydrolyze G3.</P>