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Factors Influencing the Activity and the Stability of IMP Dehydrogenase of Rat Liver
흰쥐 간 IMP 탈수소 효소의 활성과 안정도에 영향을 주는 인자

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Authors
Juhnn, Yong-Sung
Issue Date
1989-06
Publisher
Seoul National University College of Medicine
Citation
Seoul J Med, Vol.30 No.2, pp. 79-87
Keywords
IMP dehydrogenaseRat liverActivity and stability
Abstract
IMP dehydrogenase is the key enzyme in the biosynthesis of guanine nucleotides,
and is known to have close relationship with many biological phenomena including
malignant transformation. Its inhibitors have been utilized in attempt to interrupt the growth
of cancer cells and viruses. This experiment was performed to define the conditions for assay
of IMPO activity and puriftcation of the enzyme by elucidating the effect of various factors on
its activity and stability. The enzyme was prepared from partially hepatectomized rat liver by
treatment with ammonium sulfate and OEAE-celluiose chromatography. The enzyme exhibited
maxium activity at pH 7.0 and sharp decrease in its activity below and above pH 7.0.
The enzyme required free sulfhydryl groups such as mercaptoethanol and dithioerythritol for
its full activity, and mercaptoethanol inhibited 1MPO activity at the concentration above 10
mM. Among the monovalent cations tested, both K+ and Na + manifested activating effect in
contrast with the inhibitory effect of Li+, and the activating effect of sodium was only about
half the effect of potassium. All the divalent cations such as Mg2
'. Ca2 +, Cu2 +, Zn2 +
exhibited strong inhibitory effect on IMPO activity. EOTA was added to the buffers to inhibit
various phosphatases and also to remove any trace divalent actions, and did not exert any
inhibitory effect on IMPO activity. Glycerol added to purification buffers to mimic intracellular
environment manifested slightly inhibitory effect at 10% concentration, but the ethanol
showed relatively strong inhibition. As the duration of dialysis increased, the IMPD activity
was increased proportionally until 24 hours. And ammonium sulfate used for salting out
IMPD also showed strong inhibitory effect, therefore complete removal of the salt are required
before assaying the activity. When IMPD preparation was stored at ~60'C. ~20C.
4°C, and 25°C for 7 days, only the preparation stored at ~ 60"C retained most of the initial
activity, and that stored at 25°C lost most of its activity in 24 hours. Thiols such as
dithioerythritol and mercaptoethanol exhibited stabilizing effect on IMPD stored at 4('C, and
K+, glycerol, and EDTA did not show any protective effect Change of Tris buffer (pH 7.4)
buffer neither to phosphate nor to pH 8.0 improved the stability of IMPD.
ISSN
0582-6802
Language
English
URI
https://hdl.handle.net/10371/5538
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College of Medicine/School of Medicine (의과대학/대학원)Dept. of Medicine (의학과)The Seoul Journal of MedicineThe Seoul Journal of Medicine Vol. 30 No.2 (1989)
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