Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.1.1.1 (alcohol dehydrogenase)
 9,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Protein carboxyl methyltransferase and protein methylesterase activity was assayed in various cell fractions prepared from rat livers. Significant amounts of protein carboxyl methyltransferase were detected in the cytosol and nucleoplasm. The cellular concentration of this enzyme paralleled development, activity being highest in the liver from young animals. If methylation was inhibited at any point during the reaction with S-adenosylhomocysteine, protein methylesterase activity was evident by a rapid decrease in carboxyl-methylated proteins. Protein methylesterase activity could be assessed by measuring the amount of [3H]methanol present in reaction filtrates. After a 10-min lag, the rate of demethylation was equivalent to the rate of methylation. The turnover of methyl groups was primarily enzymatic, since little or no methanol was generated when adrenocorticotropic hormone was incubated with purified protein carboxyl methyltransferase. Assessment of protein methylesterase activity as a function of the amount of methanol in the reaction filtrates represents minimal values, since the resultant [3H]methanol was metabolized rapidly via an alcohol dehydrogenase and/or oxidase. The rapid turnover of the protein methyl esters makes it difficult to assess the endogenous methyl acceptor proteins. Protein methyl esters were not detectable in any significant amounts in hepatic cell fractions in vivo; however, the nuclei contained measurable amounts of carboxyl-methylated proteins in vitro. These proteins are firmly bound to DNA but are not an integral part of the nucleosome. Analysis of the proteins, after fractionation on hydroxylapatite and sodium dodecyl sulfate-acrylamide gel electrophoresis, revealed that several non-histone chromosomal proteins were carboxyl methylated. The approximate molecular weights of these proteins were 172K, 106K, 98K, 81K, 66K, 62K, 52K, and 38K.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Protein carboxyl methylation-demethylation system in developing rat livers. 300 Apr 39

The in vitro carboxyl methylation-demethylation of exogenous and endogenous proteins was investigated in rapidly proliferating thymocytes. Of all the cell fractions tested protein carboxyl methyltransferase activity was highest in the nucleoplasmic fraction (3.2 pmol/mg per minute with ACTH and 0.8 pmol/mg per minute with endogenous substrates). The only other fraction with significant activity was the cytosol (1.2 pmol/mg per minute with ACTH). The nuclei from thymocytes are extremely large; consequently some 70-80% of protein carboxyl methyltransferase in these cells is of nuclear origin. The cellular concentration of protein carboxyl methyltransferase and methyl acceptor proteins paralleled the development of the thymus. Mature lymphocytes contained about 25% of the activity of immature thymocytes. Failure to accumulate protein methyl esters, either in vitro in in vivo, was most likely due to the presence of a very active protein methylesterase. This rapid turnover of protein methyl esters was manifest by the continuous production of [3H]methanol when soluble fractions were incubated with S-adenosyl-L-[methyl-3H]methionine ([methyl-3H]AdoMet). [3H]Methanol production was enhanced upon the further addition of the particulate fractions, particularly chromatin. The turnover of protein methyl esters was primarily enzymatic, since no [3H]methanol was formed when ACTH was incubated with AdoMet and purified protein carboxyl methyltransferase. Utilizing [3H]methanol formation as an index of the rate of protein methylation-demethylation would yield minimal values, since this compound was oxidized via alcohol dehydrogenase or oxidase in these cells. The majority of the methyl acceptor proteins were located in the nuclei. The rapid methylation-demethylation of these proteins may play some role in development and (or) differentiation.
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PMID:Protein carboxyl methylation-demethylation in rat thymocytes. 407 25