Rat liver nuclear N-acetyltransferases: separation of two enzymes with both histone and spermidine acetyltransferase activity

PR Libby - Archives of biochemistry and biophysics, 1980 - Elsevier
PR Libby
Archives of biochemistry and biophysics, 1980Elsevier
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− 4 m; apparent Michaelis constants for
acetyl coenzyme A were 1.5× 10− 5 and 10− 5 m for enzymes A and B, respectively. At low …
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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