• 대한수의학회지
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• 제34권4호
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• pp.781-785
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• 1994

Uridine diphosphate(UDP)-galactose-4-epimerase-less mutants of Salmonella pullorum were isolated after mutagenic treatment with ethidium bromide. When isolated gal E mutants of S. pullorum A2 and D1 were grown in the presence of galactose(0.1 W/V), they exhibited marked bacteriolysis in heart infusion broth. The mutant strains were further investigated the characteristics of enzymatic activities in the Leoloir galactose pathway. Isolated A2 and D1 strains were completely deficient in UDP-galactose-4-epimerase activity. And the activity of other enzymes involved in galactose metabolism were reduced significantly.

• BMB Reports
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• 제43권6호
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• pp.419-426
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• 2010

Aeromonas hydrophila is a bacterial pathogen that infects a large number of eukaryotes, including humans. The UDP-galactose 4'-epimerase (GalE) catalyzes interconversion of UDP-galactose to UDP-glucose and plays a key role in lipopolysaccharide biosynthesis. This makes it an important virulence determinant, and therefore a potential drug target. Our earlier studies revealed that unlike other GalEs, GalE of A. hydrophila exists as a monomer. This uniqueness necessitated elucidation of its structure and active site. Chemical modification of the 6xHis-rGalE demonstrated the role of histidine residue in catalysis and that it did not constitute the substrate binding pocket. Loss of the 6xHis-rGalE activity and coenzyme fluorescence with thiol modifying reagents established the role of two distinct vicinal thiols in catalysis. Chemical modification studies revealed arginine to be essential for catalysis. Site-directed mutagenesis indicated Tyr149 and Lys153 to be involved in catalysis. Use of glycerol as a cosolvent enhanced the GalE thermostability significantly.

• Journal of Microbiology and Biotechnology
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• 제9권4호
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• pp.393-397
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• 1999

The gene (galE) encoding UDP-galactose-4-epimerase, operative in the galactose metabolic pathway, was cloned together with the $\beta$-galactosidase gene (lacZ) from Lactococcus lactis ssp. lactis ATCC7962 (L. lactis 7962). galE was found to have a length of 981 bps and encoded a protein with a molecular mass of 36,209 Da. The deduced amino acid sequence showed a homology with GalE proteins from several other microorganisms. A Northern analysis demonstrated that galE was constitutively expressed by its own promoter. When galactose or lactose was added into medium, the galE transcription was induced by several upstream promoters. The structure of the gal/lac operon of L. lactis 7962 was partially characterized and the gene order around galE was galT-lacA-lacZ-galE-orfX.

• KSBB Journal
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• 제23권6호
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• pp.474-478
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• 2008

효율적인 UDP-glucose regeneration system을 구축하기 위해서 재순환 시스템에 관여하는 4가지 효소 (UDP-glucose pyrophosphorylase, UDP-Kinase gene, UDP-galactose 4-epimerase, and $\beta$-1, 4-galactasyltrasnsferase)들을 E. coli AD202에서 발현 시켜 Disaccharide 합성 정도를 보았다. Disaccharide는 0.5 mM IPTG 농도에서 가장 높은 농도를 나타내었다. 대조구와 비교한 결과 LacNAc 농도는 1.34 mM로 10배 정도 정가하였고, lactose 농도는 0.39 mM로 대조구보다 2.6배 증가하였다. 총 disaccharide 농도는 1.73 mM 이며, 대조구 보다 6.5배 높은 생산성을 보였다. 본 논문은 결과는 metabolic flux regeneration으로 disaccharides 합성을 증가시킬 수 있다는 것을 보여주었다.

• Journal of Microbiology and Biotechnology
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• 제12권2호
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• pp.217-221
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• 2002

dTDP-D-glucose 4,6-dehydratase (TDPDH) catalyzes the conversion of dTDP-D-glucose to dTDP-4-keto-6-deoxy-D-glucose, and requires $NAD^＋$ as a coenzyme for its catalytic activity. The dTDP-D-glucose 4,6-dehydratase from Streptomyces antibioticus $Tu{\ddot}99$ tightly binds $NAD^＋$ [19]. In order to determine the role of lysine-148 in the $NAD^＋$ binding, the lysine of the dTDP-D-glucose 4,6-dehydratase from Streptomyces antibioticus $Tu{\ddot}99$ was mutated to various amino acids by site-directed mutagenesis. The catalytic activity of the four mutated enzymes of TDPDH did not recover after addition of $NAD^＋$ . However, the activity of K159A, the mutated enzyme of UDP-D-glucose 4-epimerase (UDPE), recovered after the addition of $NAD^＋$ [15]. Although dTDP-glucose 4,6-dehydratase, and UDP-galactose (glucose) 4-epimerase are members of the short-chain dehydrogenase/reductase SDR family and the lysine-148 of TDPDH was highly conserved as in UDPE (Lys-159), the function of the lysine-148 of TDPDH was different from that of UDPE. The mutated enzymes showed that the lysine-148 of the dTDP-D-glucose 4,6-dehydratase played no role in the $NAD^＋$ binding. Accordingly, it is suggested that the lysine-148 of the dTDP-D-glucose 4,6-dehydratase is involved in the folding of TDPDH.

• Asian-Australasian Journal of Animal Sciences
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• 제33권11호
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• pp.1725-1731
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• 2020

Objective: An initial RNA-Sequencing study revealed that UDP-galactose-4-epimerase (GALE) was one of the most promising candidates for milk protein concentration in Chinese Holstein cattle. This enzyme catalyzes the interconversion of UDP-galactose and UDP-glucose, an important step in galactose catabolism. To further validate the genetic effect of GALE on milk protein traits, genetic variations were identified, and genotypes-phenotypes associations were performed. Methods: The entire coding region and the 5'-regulatory region (5'-UTR) of GALE were re-sequenced using pooled DNA of 17 unrelated sires. Association studies for five milk production traits were performed using a mixed linear animal model with a population encompassing 1,027 Chinese Holstein cows. Results: A total of three variants in GALE were identified, including two novel variants (g.2114 A>G and g.2037 G>A) in the 5'-UTR and one previously reported variant (g.3836 G>C) in an intron. All three single nucleotide polymorphisms (SNPs) were associated with milk yield (p<0.0001), fat yield (p = 0.0006 to <0.0001), protein yield (p = 0.0232 to <0.0001) and protein percentage (p<0.0001), while no significant associations were detected between the SNPs and fat percentage. A strong linkage disequilibrium (D' = 0.96 to 1.00) was observed among all three SNPs, and a 5 Kb haplotype block involving three main haplotypes with GAG, AGC, and AGG was formed. The results of haplotype association analyses were consistent with the results of single locus association analysis (p<0.0001). The phenotypic variance ratio above 3.00% was observed for milk protein yield that was explained by SNP-g.3836G >C. Conclusion: Overall, our findings provided new insights into the polymorphic variations in bovine GALE gene and their associations with milk protein concentration. The data indicate their potential uses for marker-assisted breeding or genetic selection schemes.

• 대한유전성대사질환학회지
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• 제13권2호
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• pp.89-97
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• 2013

Purpose: We retrospectively investigated individuals who hadbeen identified by neonatal screening as potential galactosemia patients to determine the etiology of galactosemia. Methods: One hundred fifty-three patients referred to Korea Genetics Research Center due to high galactose level detected by neonatal screening test between February 2005 and May 2013 were examined. Galactose and galactose-1-phosphate levels were measured by using a fluoro metric microplate reader. Lactose free diet was initiated immediately after confirmed by urine Clinitest. If reducing sugar was negative, we employed abdominal sonogram and echocardiogram to check for possible porto-systemic shunt. Results: Fifteen patients were diagnosed with galactosemia. One patient had galactokinase (GALK) deficiency; four had UDP galactose-4-epimerase (GALE) deficiency; two had citrin deficiency; and four had porto-systemic shunt. Two had unknown causes of galactosemia. Conclusion: In addition to genetic defects of GALT, GALK and GALE, citrin deficiency or porto-systemic shunt could also cause galactosemia. It is crucial to carry out differential diagnosis to determine the cause of galactosemia.

• 대한유전성대사질환학회지
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• 제16권3호
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• pp.135-140
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• 2016

Purpose: Galactose is metabolized to galactose-1-phosphate by galactokinase (GALK), galactose-1-phosphate uridyltransferase (GALT) and UDP-galactose-4-epimerase (GALE), and galactosemia occurs when each enzyme is deficient. In Korea, unlike foreign countries, classic galactosemia is rare and transient galactosemia due to GALK hyperactivity is reported, but studies on frequency, clinical significance, and genetic variation are lacking. In this study, we analyzed the clinical characteristics of patients with galactosemia due to GALK hyperactivity. Methods: We investigated 85 patients who had an elevated galactose level in the neonatal screening test without deficiency of enzymes at Department of Pediatrics, Seoul & Bucheon Soonchunhyang University Hospital from January 2008 to June 2016. We investigated the level of galactose, galactose-1-phosphate, GALK and duration of galactose normalization, and analyzed the correlation between GALK elevation and galactose, galactose-1-phosphate and duration of galactose normalization. And the levels of galactose, galactose-1-phosphate, and duration of galactose normalization were compared between the galactose-free formula feeding group and non-feeding group. Results: Mean age of visit was $26.7{\pm}16.1days$. Duration of galactose normalization was $35.3{\pm}20.5days$. Mean galactose level was $18.5{\pm}7.3mg/dL$ in the neonatal screening and follow-up galactose level in serum was $2.3{\pm}5.4mg/dL$. The mean value of galactose-1-phosphate was $6.0{\pm}4.7mg/dL$ and the mean GALK level was $3.84{\pm}1.28{\mu}mol/Hr/gHb$. There was no significant correlation between GALK levels and galactose levels in the neonatal screening test (P=0.351), and we analyzed the correlation between GALK levels and follow-up galactose levels in serum, there was no significant correlation (P=0.101). There was a significant correlation between GALK levels and galactose-1-phosphate (P=0.015), and the correlation between GALK levels and duration of galactose normalization was not statistically significant (P=0.176). 49% of the patients were fed galactose-free formula, and 45% were not. Galactose and galactose-1-phosphate levels in the neonatal screening test were statistically significantly higher (P=0.004, 0.034) in using galactose-free formula group. Duration of galactose normalization was not related to the use of galactose-free formula (P=0.266, 0.249). Conclusion: Galactosemia due to GALK hyperactivity seems to be a temporary phenomenon and may not require galactose restriction. More research is needed on the role of the nuclear protein, racial traits and genetic variations in Korean patients.

• Clinical and Experimental Pediatrics
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• 제46권5호
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• pp.440-446
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• 2003

목 적 : 갈락토스혈증은 유전성 대사 질환으로 상염색체 열성으로 유전되며 대표적으로 세 효소의 결핍에 의거하며 임상적 양상은 갈락토스에 대해 노출되면서 증상이 나타난다. 첫째는 GALT 결핍증, 둘째는 GALK 결핍증이고, 셋째는 GALE 결핍증이다. 현재 우리 나라에서 출생 후 갈락토스혈증에 대한 신생아 선별검사를 시행하고 있다. 우리 나라의 갈락토스혈증의 양상에 대해 알아보기 위해 저자들은 신생아기에 시행한 선별검사에서 이상소견을 보여 정밀검사를 시행하여 진단된 갈락토스혈증 환자에 대해 보고하는 바이다. 방 법: 신생아 선별검사에서 이상소견을 보여 생후 1개월에 순천향대학병원 소아과에서 정밀검사를 시행하여 갈락토스혈증이 확진된 환아들의 외래 및 입원 기록을 후향적으로 검토하였다. 내원 당시 갈락토스혈증을 확진하기 위해 갈락토스를 효소비색법과 형광측정법으로 측정하였고, 형광측정법으로 galactose-1-phosphate를 측정하였다. 적혈구 내의 GALK, GALT, GALE의 활성도, 그리고 galactose-1-phosphate를 동위원소 검사로 측정하였으며 Beutler 법을 시행하였다. 진단된 환아들에서는 유당제거 식이를 투여하면서 갈락토스와 galactose-1-phosphate를 추적검사 하였으며 의심되는 효소에 대한 추적 검사도 시행하였다. 결 과: 갈락토스혈증으로 확진받은 환아들은 총 10명이었고 그 중 남아가 6명, 여아가 4명이였다. 10명 중 GALK 결핍증이 2명, GALT 결핍증이 2명 그리고 GALE 결핍증이 6명으로 GALE 결핍증이 가장 많았다. 2명에서 GALK 결핍증이 진단되었으며 GALT와 GALE은 두 환아 모두에서 정상이면서 GALK가 각각 0.7, 8.02 nmol/min/g Hb로 감소되어 있어 GALK 결핍증으로 진단하였다. 1명의 환아의 경우 GALK가 심하게 감소되어 있었으며 2번 환아의 경우 2세와 3세에 추적 검사한 GALK가 각각 16.7, 16.8 nmol/min/g Hb로 1세 이후의 정상치인 20-30 보다 낮았으며 감소 정도로 보아 보인자로 생각되었다. GALT 결핍증의 경우 2명의 환아에서는 적혈구 내의 GALT의 활성도가 각각 6.7, $8.6{\mu}L/hr/g$ Hb로 정상보다 감소되어 있어 GALT 결핍증으로 진단하였으며 두 환아 모두 DNA분석에서 Duarte 2/G(galactosemia)의 유전형을 갖는 Duarte 2 variant galactosemia로 진단되었다. GALE 결핍증이 7명으로 가장 많았으며 GALE의 활성도는 6명 모두에서 정상보다 감소되어 있었다. 이들 중 3명은 적혈구 내의 GALE의 활성도가 진단시 각각 14.9, 9.2 $8.6{\mu}L/hr/g$ Hb이었고 추적 검사한 GALE의 활성도는 각각 14.8, 12.7, $12.21{\mu}L/hr/g$ Hb로 이들의 감소정도로 보아 GALE 결핍증 중 경증 또는 보인자로 생각되었다. 1명은 진단시 및 추적 검사한 GALE의 활성도가 각각 2.9, $6.46{\mu}L/hr/g$ Hb로 감소 정도로 보아 homozygote state로 추정되었다. 또한 다른 1명은 GALE의 활성도가 $6.8{\mu}L/hr/g$ Hb로 감소 정도로 보아 homozygote state로 추정되나 앞으로 추적 검사가 필요할 것으로 사료된다. 그 외에 4명의 환아들의 경우 효소의 결핍에 의한 갈락토스혈증이 아니라 GALK의 과다반응에 의해 갈락토스가 증가하는 소견을 보였다. 그러므로 갈락토스 농도가 증가하였을 때 GALK 과다반응의 경우를 감별해야한다. 결 론 : 본 연구의 경우 임상적으로 증상이 있었던 경우는 없었으며 GALE 결핍증이 가장 많았고 GALT 결핍증 환아들은 모두 보인자였다. 또한 유당 제거 식이 후 갈락토스와 galactose-1-phosphate는 정상 범위를 유지하였다. 신생아 선별검사를 통해 갈락토스혈증이 의심되는 경우 정밀검사를 통해 확진을 하여 갈락토스혈증이 어떤 병형인가를 알아내는 것이 예후에 중요하며 조기 치료를 하는 것이 필요하다.

• Journal of Applied Biological Chemistry
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• 제64권3호
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• pp.309-316
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• 2021

Trifolin (kaempferol 3-O-galactoside)는 플라보놀 그룹에 속하는 물질로 아토피, 항균, 폐암에 효과가 있는 것으로 알려져 있다. Trifolin은 다양한 식물에서 추출하여 사용하고 있지만 추출 과정이 복잡하고, 수율이 낮으며, 추출을 위한 바이오매스를 얻는데 계절적 어려움이 있다. 생물전환은 저렴한 화합물에서 고부가가치 화학물질을 생산할 수 있는 대체 수단으로 이용된다. 본 연구에서는 naringenin으로부터 trifolin을 생합성하기 위해 3개의 유전자(PeFLS 및 OsUGE-PhUGT)를 각각의 대장균에 도입한 BL-FLS균주와 BL-UGTE균주를 이용하여 공조배양시스템을 개발하였다. Naringenin으로부터 trifolin을 생합성하기 위해 세포의 밀도, 생물전환 온도, 재조합 단백질 유도의 적정 IPTG농도 및 시간, 기질 공급 농도 등의 최적화를 실시하였다. 최적화된 공동 배양 발효 시스템을 통해 67.3 mg/L의 trifolin을 성공적으로 생합성 하였다.