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RISS 인기검색어
- 검색키워드
- 저자 : 김두식 ( Soo Young Choi (검색결과 4 건)
- 무료
- 기관 내 무료
- 유료
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Catalytic and Structural Properties of 4-Aminobutyrate Aminotransferase
최수영,김두식,Choi, Soo-Young,Kim, Doo-Sik 생화학분자생물학회 1991 한국생화학회지 Vol.24 No.5
4-Aminobutyrate aminotransferase(GABA transaminase)는 lysyl group에 특이한 Bis-PLP나 -SH group에 특이한 DTNB 또는 DPD에 의하여 효소가 불활성화 되었으며 이 불활성화는 효소의 기질인 ${\alpha}$-ketoglutarate의 결합부위에 lysyl group과 cysteinyl group이 위치하고 있음을 보여주는 것이다. GABA transaminase의 second catalytic site에 대한 구조적 특성을 밝히기 위하여 native 효소를 $NaBH_4$로 환원시킨 후 몇 가지 아미노산 기질을 이용하여 kinetic parameters를 조사해 본 결과 큰 차이가 없음을 알 수 있었다. 이는 second catalytic site가 구조적으로나 작용기적으로 native 효소의 catalytic site와 같다는 것을 나타낸다. 마지막으로 native 효소에서 cofactor가 떨어졌을 때(apo 효소) 구조적 변화를 가져왔다. 이는 효소가 in vivo에서 합성될 때 불안정한 apo enzyme으로 만들어진 후 cofactor가 binding 함으로써 촉매 기능적으로 또는 구조적으로 안정화 된다고 본다. 4-Aminobutyrate aminotransferase (GABA transaminase) was inactivated by either lysyl or sulfhydryl reagents. The inhibitory effect was protected by ${\alpha}$-ketoglutarate, one of the substrate of GABA transaminase. These are powerful evidence that lysyl and cysteinyl residues are located in catalytic domain of the enzyme. The function of the second catalytic site of the enzyme was also examined. After reduction with $NaBH_4$ followed by cofactor reconstitution, the reduced enzyme was capable of catalyzing transamination reaction of the amino substrate, such as 4-aminobutyrate, ${\beta}$-alanine or 5-aminovalerate. Since there is no significant difference in the catalytic parameter between the native and reduced enzymes, it seems reasonable to conclude that the additional catalytic site is functionally identical to the catalytic site of the native enzyme. Moreover, apoenzyme undergoes conformational changes upon binding of cofactor pyridoxal-5-phosphate (PLP) which indicates that apoenzyme becomes conformationally stabilized as a consequence of the cofactor binding.
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4 - Aminobutyrate aminotransferase 의 촉매기능과 구조적 특성
최수영,김두식 ( Soo Young Choi,Doo Sik Kim ) 생화학분자생물학회 1991 BMB Reports Vol.24 No.5
4-Aminobutyrate aminotransferase (GABA transaminase) was inactivated by either lysyl or sulfhydryl reagents. The inhibitory effect was protected by α-ketoglutarate, one of the substrate of GABA transaminase. These are powerful evidence that lysyl and cysteinyl residues are located in catalytic domain of the enzyme. The function of the second catalytic site of the enzyme was also examined. After reduction with NaBH₄followed by cofactor reconstitution, the reduced enzyme was capable of catalyzing transamination reaction of the amino substrate, such as 4-aminobutyrate, β-alanine or 5-aminovalerate. Since there is no significant difference in the catalytic parameter between the native and reduced enzymes, it seems reasonable to conclude that the additional catalytic site is functionally identical to the catalytic site of the native enzyme. Moreover, apoenzyme undergoes conformational changes upon binding of cofactor pyridoxal-5-phosphate (PLP) which indicates that apoenzyme becomes conformationally stabilized as a consequence of the cofactor binding.
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GABA transaminase 의 새로운 보조인자 유사체로서의 6 - Br - pyridoxal - 5 - phosphate
최수영,위세찬,김두식 ( Soo Young Choi,Sechan Wee,Doo Sik Kim ) 생화학분자생물학회 1989 BMB Reports Vol.22 No.2
6-Br-pyridoxal-5-phosphate, a new cofactor analog of pyridoxal-5-phosphate, was synthesized and purified homogeneously by organic and enzymatic methods. This cofactor analog binds to cofactor binding site of GABA transaminase. Resolved and reduced GABA transaminase restore the catalytic activity by 6-Br-PLP. These results indicate that the 6-Br-PLP remains covalently attached to the amino acid residue of the catalytic site and acts like natural cofactor.
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6-Br-Pyridoxal-5-Phosphate a New Cofactor Analog of GABA Transaminase
최수영,위세찬,김두식,Choi, Soo-Young,Wee, Se-Chan,Kim, Doo-Sik 생화학분자생물학회 1989 한국생화학회지 Vol.22 No.2
여러 효소의 자연적인 보조인자인 pyridoxal-5-phosphate의 새로운 유사체로서 6-Br-pyridoxal-5-phosphate를 유기합성과 효소를 이용한 합성방법에 의해 순수분리 정제하였다. 자외선 흡수 또는 형광 분광법에 의해 이 보조인자 유사체는 신경조직에서 신경전달물질의 하나로 알려진 GABA (4-aminobutyate)의 분해효소인 GABA transaminase의 보조인자 결합자리에 붙어서 resolved 또는 reduced GABA transaminase의 효소 활성도를 복구시켰다. 이러한 사실들은 6-Br-PLP가 GABA transaminase의 catalytic site에 있는 아미노산과 공유결합을 하여 자연적인 보조인자와 같은 역할을 한다고 볼 수 있다. 6-Br-pyridoxal-5-phosphate, a new cofactor analog of pyridoxal-5-phosphate, was synthesized and purified homogeneously by organic and enzymatic methods. This cofactor analog binds to cofactor binding site of GABA transaminase. Resolved and reduced GABA transaminase restore the catalytic activity by 6-Br-PLP. These results indicate that the 6-Br-PLP remains covalently attached to the amino acid residue of the catalytic site and acts like natural cofactor.
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