Protein methylase I ( S?adenosyl ? L ?methionine : protein?arginine methyltransferase, EC 2.1.1.23) having an optimal pH at around 7.3 was purified 117 fold with a 31 % recovery from snake head liver.´Ihe enzyme showed a optimum temperature at around 31°C and was completely inactivated at 43°C.
Both histone type II?A and histone type Wi?S were verified as good substrates in accepting methyl group from S?adenosyl ?L? methionine, whereas histone type Ill?S, egg albumin, r?globulin, bovine serum albumin. And lysozyme were poor.
The Km value for S?ade;;asyl?L?methionine was 6.75 x 10´ M at 37 C and the maximum velocities were 47.6 and 84.8 pmole/mir./mg protein at 21 t and 31 C respectively so that the activation energy of the enzyme was calculated as 21.76 kJ/mole.
Copper and zinc ions were the potent inhibitor, and the inhibitory effect were 43.5 % and 33.8% of total activity at 200uM respectively. Sulfate ion also acted as an inhibitor, showing 50% of this enzyme activity at 160mM. Protein methylase I was not only activated but also stabilized the presence of ammonium ion
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