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RISS 인기검색어
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- 저자 : 홍순근 ( Doo Ha Kim (검색결과 3 건)
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Inactivation Kinetics of ${\beta}$-D-galactosidase
김두하,한영희,홍순근,Kim, Doo-Ha,Hahn, Young-Hee,Hong, Soon-Keun 생화학분자생물학회 1982 한국생화학회지 Vol.15 No.1
효소의 불활성화 속도상수를 결정하는 새로운 측정방법을 고안하였으며, ${\beta}$-D-galactosidase (EC. 3.2.1.23)의 열변성에 있어서 수소이온 농도 및 초기효소농도 변화에 따른 효소불활성화의 작용기전을 규명하는데 이 방법을 적용하였다. 효소 불활성화 속도상수와 효소활성의 반감기는 효소반응을 진행시키면서 열에 의하여 불활성화를 유도할때 나타나는 흡광도의 증가를 연속적으로 기록 한 다음, 이동안 기질농도의 변화가 무시될 수 있을때는 점근회기방법에 의하여 이효소의 불활성화 속도상수를 결정할 수 있었다. 효소분자끼리 회합하지 않고, 소분자 물질, 예를들면 금속이온, 기질 및 수소이온등이 효소분자와 결합하여 이들이 평형상태를 이루고 각 결합형들이 서로 다른 반응속도로 불활성화 될 때는 불활성화 속도상수는 효소농도에는 무관하고 단지 결합하는 소분자들에 의해서만 영향을 받음을 수소이온의 경우를 통하여 확인하였다. 이 효소의 불활성화 속도상수는 반응액의 수소이온 농도가 감소함에 따라서 계단식으로 증가함이 관찰되었으며, 이것은 4가지 형태의 이온화한 효소의 중간체를 가정하면 이론적으로 설명할 수 있었다. 따라서 서로 다른 3가지 종류의 아마노산 측쇄가 이효소의 안정성에 크게 관여한다는 것을 알 수 있었다. 이효소의 불활성화 반응차수는 효소의 농도가 증가함에 따라서 연속적으로 증가하였으며, 효소농도에 따른 불활성화 반응차수는 온도에 크게 영향을 받음을 알 수 있었다. 본연구의 실험조건에서는 반응차수가 1에서 2까지 증가하였다. 이때 겉보기 불활성화 반응속도상수는 효소의 어떤 농도를 기준으로 하여 그보다 묽어질때는 급격히 증가하였으며 그보다 진한 농도에서는 완만하게 증가함을 보여주었다. 이현상은 효소의 2분자 또는 3분자 간의 회합을 가정하면 설명이 가능하였다. An improved method of determining the rate constant of an enzyme inactivation was successfully applied to the kinetic study of thermal inactivation of ${\beta}$-D-galactosidase (EC. 3.2.1.23) concerning the hydrogen ion concentration and the initial concentration of the enzyme. The rate constant and halflife of the enzyme could be determined conveniently from the recorded data of absorbance during inactivation by the asymptotic regression method when the substrate depletion could be neglected. The rate constant of inactivation was dependent on the ligand molecules such as metal cofactors, substrate concentration and proton concentration etc. Under the assumption of equilibrium state between each complexed form of different inactivation rate constant, kinetic equations of the apparant rate constant could be derived and applied to the $H^+$ concentration. The rate constant of inactivation increased with a double sigmoid pattern with decreasing $H^+$ concentration. And it could be explained by assuming 4 intermediates of ionized enzyme forms. This means that 3 different ionizable side chains of the enzyme contribute largely to the conformational stability of this enzyme. The reaction order of inactivation of ${\beta}$-D-galactosidase increased continuously with increasing the enzyme concentration, and it was affected by the inactivation temperature. In this work, it increased from 1 to about 2. The apparant rate constant increased sharply with decreasing the enzyme concentration below a critical value but it increased slowly with increasing the enzyme concentration above the critical point. This could be successfully explained by a dimerization model and trimerization model as suggested in this work.
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β - D - galactosidase 불활성화에 대한 동력학적 연구
김두하,한영희,홍순근 ( Doo Ha Kim,Young Hee Hahn,Soon Keun Hong ) 생화학분자생물학회 1982 BMB Reports Vol.15 No.1
An improved method of determining the rate constant of an enzyme inactivation was successfully applied to the kinetic study of thermal inactivation of β-D-galactosidase (EC. 3.2.1.23) concerning the hydrogen ion concentration and the initial concentration of the enzyme. The rate constant and halflife of the enzyme could be determined conveniently from the recorded data of absorbance during inactivation by the asymptotic regression method when the substrate depletion could be neglected. The rate constant of inactivation was dependent on the ligand molecules such as metal cofactors, substrate concentration and proton concentration etc. Under the assumption of equilibrium state between each complexed form of different inactivation rate constant, kinetic equations of the apparant rate constant could be derived and applied to the H^+ concentration. The rate constant of inactivation increased with a double sigmoid pattern with decreasing H^+ concentration. And it could be explained by assuming 4 intermediates of ionized enzyme forms. This means that 3 different ionizable side chains of the enzyme contribute largely to the conformational stability of this enzyme. The reaction order of inactivation of β-D-galactosidase increased continuously with increasing the enzyme concentration, and it was affected by the inactivation temperature. In this work, it increased from 1 to about 2. The apparant rate constant increased sharply with decreasing the enzyme concentration below a critical value but it increased slowly with increasing the enzyme concentration above the critical point. This could be successfully explained by a dimerization model and trimerization model as suggested in this work.
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이동권(Dong Kwon Rhee),임창진(Chang Jin Lim),김두하(Doo Ha Kim),홍순근(Soon Keun Hong),박은희(Eun Hee Park),한용남(Yong Nam Han) 大韓藥學會 1982 약학회지 Vol.26 No.4
Acute toxicities of purified ginseng saponin (PGS) in mice, and subacute toxicities of PGS in rats were investigated. Average lethal doses (LD50) of PGS in male mice were 270mg/kg (i.v.), 342mg/kg (i.p.), 505mg/kg (i.m.), 950mg/kg (s.c.), and more than 5,000mg/kg (p.o.), respectively. Results of subacute toxicity of PGS was as follows. Body weight was markedly increased by administration of PGS 7.7mg/kg but side effects were shown by administration of 77mg/kg and above dose. Especially administration of PGS 240mg/kg caused a marked decrease of albumin/globulin ratio, and 28% increase of urea nitrogen in serum, as well as 33% increase of liver weight/body weight ratio.
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