• Journal of the Korean Wood Science and Technology
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• 제30권1호
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• pp.63-71
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• 2002

사시나무속의 현사시, 이태리포플러 및 양황철나무 수피를 아세톤-물(7:3)로 추출한 후 농축하고 헥산, 클로로포름, 에틸아세테이트 및 수용성으로 분획하여 동결건조하였다. 각 추출물은 메탄올 수용액 및 에탄올-헥산 혼합액을 사용하여 Sephadex LH-20 칼럼크로마토그래피로 화합물을 분리한 후 TBA 및 6% 초산으로 전개하는 셀룰로오스 박층크로마토그래피로 단리 여부를 확인하였다. 단리된 화합물의 구조는 ¹H, ¹³C 및 2D-NMR과 질량분석에 의하여 결정되었다. 사시나무속 수종의 추출성분은 주로 flavonoid와 salicin 파생물로 구성되어 있으며 세 종류의 수종에서 모두 15개의 화합물이 분리되었다. 현사시나무에서는 (+)-catechin, naringenin, eriodictyol, sakuranetin, aromadendrin, taxifolin, sakuranetin-5-O-𝛽-D-glucopyranoside. neosaturanin. p-coumaric acid, salireposide와 aesculin이 단리되어 가장 많은 종류의 화합물을 포함하고 있었으며 이태리포플러에서는 (+)-catechin, salireposide, populoside와 salicortin이, 양황철나무에서는 (+)-catechin, padmatin, quercetin, salireposide, populoside와 salicortin이 단리되었다.

• Journal of Microbiology and Biotechnology
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• 제18권5호
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• pp.901-907
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• 2008

Thermotoga neapolitana $\beta$-glucosidase (BglA) was subjected to site-directed mutagenesis in an effort to increase its ability to synthesize arbutin derivatives by transglycosylation. The transglycosylation reaction of the wild-type enzyme displays major ${\beta}(1,6)$ and minor ${\beta}(1,3)$ or ${\beta}(1,4)$ regioselectivity. The three mutants, N291T, F412S, and N291T/F412S, increased the ratio of transglycosylation/hydrolysis compared with the wild-type enzyme when pNPG and arbutin were used as a substrate and an acceptor, respectively. N291T and N219T/F412S had transglycosylation/hydrolysis ratios about 3- and 8-fold higher, respectively, than that of the wild-type enzyme. This is due to the decreased hydrolytic activity of the mutant rather than increased transglycosylation activity. Interestingly, N291T showed altered regioselectivity, as well as increased transglycosylation products. TLC analysis of the transglycosylation products indicated that N291T retained its ${\beta}(1,3)$ regioselectivity, but lost its ${\beta}(1,4)$ and ${\beta}(1,6)$ regioselectivity. The altered regioselectivity of N291T using two other acceptors, esculin and salicin, was also confirmed by TLC. The major transglycosylation products of the wild type and N291T mutant were clearly different. This result suggests that Asn-291 is highly involved in the catalytic mechanism by controlling the transglycosylation reaction.