Rat liver nuclear N-acetyltransferases: Separation of two enzymes with both histone and spermidine acetyltransferase activity |
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| Authors: | Paul R Libby |
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| Institution: | 1. Department of Experimental Therapeutics and Grace Cancer Drug Center, New York State Department of Health, 666 Elm Street, Buffalo, New York 14263 USA;2. Department of Breast Surgery, Roswell Park Memorial Institute, New York State Department of Health, 666 Elm Street, Buffalo, New York 14263 USA |
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| Abstract: | Two similar histone acetyltransferases have been separated from rat liver nuclei and purified 500-fold. Both enzymes also acetylate spermidine and spermine but diamines are not acetylated. Both enzymes preferentially acetylate histone 3; among the remaining histones H2A and H2B are good substrates, whereas H1 and histone 4 are poor substrates. Apparent Michaelis constants for spermidine were about 2 × 10?4m; apparent Michaelis constants for acetyl coenzyme A were 1.5 × 10?5 and 10?5m for enzymes A and B, respectively. At low concentrations DNA inhibits histone acetylation by enzyme A (50% inhibition at 25 μg/ml DNA). Enzyme B is relatively insensitive to DNA. This suggests the possibility of separate intranuclear localization of the two enzymes. |
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