Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.1.1.37 (DNA methyltransferase)
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DNA methyltransferase (DMase) was purified 700- and 1002-fold from normal rat liver and transplantable hepatocellular carcinoma 252 (THC 252) nuclei, respectively, using a four-step procedure that included chromatography on phosphocellulose, hydroxylapatite, DEAE-Sephacel and gel filtration on AcA 34. The enzymes had identical characteristics: pI = 7.4-7.6; Mr = 280 000 by gel filtration; preference for methylating double-stranded over single-stranded DNA and hemimethylated over unmethylated DNA templates; and apparent km of 10 microM for dinucleotide units in poly(dC-dG) and 0.5 microM for S-adenosylmethionine (SAM). Thermal inactivation profiles and sulfhydryl group alkylation inhibition curves for fraction III produced very similar single-transition curves, suggesting the presence of a single-functional enzyme species that is indistinguishable between normal and tumor tissue. Single-value Michaelis-Menten kinetics were obtained for fraction IV enzymes with respect to the concentration of SAM and dinucleotide units in poly(dC-dG), suggesting the absence of isozymic or multiple forms of DMase in normal and malignant liver tissues.
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PMID:Indistinguishable physical and catalytic properties of DNA methyltransferase from normal rat liver and a transplantable rat hepatocellular carcinoma. 400 74