Eun-Ryoung Kim graduated at the age of 25 years from Chung Buk National University and now has been in the master’s course from Kyung Hee University major in Food microbiology and biotechnology.
Amylosucrase (ASase, EC 18.104.22.168) is belonging to glycoside hydrolase family 13 (GH13) and has uncommon three enzymatic activities of hydrolysis, polymerization and isomerization. ASase acts on substrates containing α-glucoside linkages and has a catalytic mechanism named α-retaining double displacement forming glycosyl-enzyme intermediate. In this study, two kinds of recombinant ASases from Neisseria polysaccharea (NPAS) and Deinococcus geothermalis (DGAS) were used for transglucosylation on daidzin. Daidzin is known as a major isoflavone and found in Kudzu and soybean. Transglucosylation of daidzin is expected to improve water-soluble, stability of chemical structure and taste. Two similar enzymes (NPAS and DGAS) showed quite different reaction products with same substrates. While the main transglycosylation products of NPAS reaction were daidzein-7-O-β-diglucoside and daidzein-7-O-β-triglucoside, those obtained by DGAS were daidzein-7-O-β-diglucoside and daidzin isomer. These results indicated that two enzymes may have different structural spaces inside of the catalytic sites, which leading to the uncommon transglycosylation reactions.
Dong-Sup Choi graduated at the age of 25 years from Han Kyong National University and now has been in the master’s course from Kyung Hee University major in Food Microbiology and Biotechnology.
Ruminococcus bromii is considered as an important species in the human gut that degrades efficiently resistant starch (RS) that escape the digestion by host enzymes. When RS Type 3 has been used as a source of energy, R. bromii have been shown to express extracellular glycoside hydrolase (GH) enzymes. Among the extracellular GH enzymes, Amy 9 has high activity at 55℃ at pH 5 in sodium acetate and high specificity towards α-1.4-glucosidic linkages, whereas Amy 10 and Amy 12 have high activity at 40℃ at pH 5 in sodium acetate and strong activity to α-1.6-glucosidic linkage about short branched chain. Although each Amy10, Amy12 were not able to degrade RS type 3, the mixture of various extracellular enzymes with Amy 9 (Amy 9 + Amy 10 or Amy 9 + Amy 12) was higher than activity of single extracellular enzyme indicating the synergistic properties of these enzymes. Our study was conducted to understand the characterization of GH enzymes which are responsible for RS degradation and the synergistic relationship between extracellular GH proteins from R. bromii.