• Archives of Pharmacal Research
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• v.8 no.3
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• pp.149-157
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• 1985

The HCL hydrolyzate of the non-histone protein fractionated from the rat liver nuclei which have been incubated inthe presence of S-adenosyl-L-[methyl-$^{14}C$ ]-methionine shows at least four unidentified radioactive peaks on a basic amino acid analysis chromatogram. One of these unknown compounds (designated as compound 3) is also formed by the rat liver homogenated with the exogenous addition of an appropriate protein substrate. Since boiled rat liver homogenate or fresh homogenate in the absence of an exogenous protein substrate failed to form compound 3, its formation can be considered to be enzyme-catalyzed. The enzyme which yields compound 3 shows a preference of protein substrate in the order of reductively methylated hemoglobin > native > histone type II-A. The rat enzyme is nuclear in location associated with chromatin, and exhibits the highest activity in the liver among various rat organs. A compound 3-forming enzyme is also present in Neurospora crassa, since endogenous formation of the compound 3 can be demonstrated with the crude extract of this mold. The chemical identity of compound 3 is not yet known. However, it resisted to the following treatments; 6 N HCL and 0.1 N Na NaOH hydrolysis at $110^{\circ}C$, OR L-amino acid oxidase.

• YAKHAK HOEJI
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• v.35 no.6
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• pp.473-482
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• 1991

Protein methylase II (S-adenosyl-L-methionine:protein carboxyl-O-methyltransferase; EC 2.1.1.24., PM II) was purified from chicken pancreas by subcellular fractionation, DEAE-cellulose chromatography, QAE-Sephadex A-50 chromatography, Sephadex G-75 chromatography, and Sephadex G-75 rechromatography. The purified PM II gave a single band upon polyarcrylamide gel electrophoresis both in the presence of SDS and in Tris glycine buffer without SDS. The pI value of purified PM II was identified as 5.7 on isoelectric focusing gel. Properties and activities of PM II were studied and the following results were obtained. 1) PM II from chicken pancreas was purified approximately 221-fold with a yield of 1.3%. 2) The purified PM II appear constituted of a single polypeptide chain of a molecular weight 46,800 daltons. 3) Hemoglobin exhibited the highest of methyl-accepting activity among the substrates tested. 4) The purified PM II has a $K_m$ of $4.67{\times}10^{-6}M$ and a $V_{max}$ of 37.5 pmoles of $methyl-^{14}C/min./mg$ enzyme for $SAM^{-14}CH_3$ as methyl donor in the presence of histone type II-As. 5) It is found that S-adenosyl-L-homocysteine is a competitive inhibitor for PM II with $K_i$ value of $3.23{\times}10^{-5}M$.