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소 肝組織 Protein Methylase Ⅱ의 精製 및 性狀
金汶成,林圭,黃炳斗 충남대학교 의과대학 지역사회의학연구소 1986 충남의대잡지 Vol.13 No.2
Protein methylase Ⅱ(S-adenosyl-L-methionine: protein carboxyl-O-methyltransferase) has been purified from bovine liver approximatery 3,305-fold with a 9% yield by combination of ammonium sulfate precipitate, sephadex G-75 chromatography, S-adensyl-L-homocysteine sepharose 4B affinity chromatography and hydroxyapatite chromatography. 1. The enzyme shows a pH optimum around 5.8. 2. The enzyme is heat labile, inactivated by heat-treatment for 10 minutes at 60℃, and when stored at -20℃ in the presence of 10% glycerol, approxymately 80% of its activity has been lost in the 4 weeks. 3. Ferrous ion (Fe^2+) is comparatively potent inhibitor, the activity being inhibited upto 50% at 2 mM and the inhibition is almost recovered by addition of 4 mM EDTA, and cupper ion (Cu^2+) also inhibited upto 36% at 2 mM. The other ions do not almost inhibit. 4. The apparent Km for S-adenosyl-L-methionine is 1×10 exp(-5) M and kinetic analysis of the enzyme in the presence of 1 mM ferrous ion shows that the nature of the inhibition to the enzyme is competitive, considering that Vmax is independent while Km is increased. 5. Histone IIA, histone H3 and IgG are relatively good substrates for the enzyme. 6. The enzyme activity is completely inhibited by 0.5 mM of p-hydroxymercuribenzoic acid (PHMB), but all of the activity is recovered in adding 10 mM mercaptoethanol. 7. The molecular weight of the enzyme is 22,000. And the properties such as above results of protein methylase Ⅱ of bovine liver are compared with those of protein methylase Ⅱ of the other tissues.