Properties of N-Acetylhistamine Deacetylase in Mammalian Brain

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Abstract
Properties of N-acetylhistamine deacetylase in rat brain were studied, utilizing a sensitive coupled radioenzymatic assay. The Km for N-acetylhistamine for this deacetylase was 660 .mu.M and its Vmax was 330 pmol/h per mg protein. N-Acetylhistamine deacetylase activity increased 80% in the presence of 1 mM Mn2+. The Km of Mn2+ was 40 .mu.M. The enzyme is primarily a soluble enzyme with a relatively uniform regional distribution, unlike the distribution for histamine and histidine decarboxylase. Neonatal activity of this enzyme in rat brain is higher than in adult brain. .alpha.-Fluoromethylhistidine does not affect the activity of N-acetylhistamine, indicating that deacetylation probably does not play a regulatory role in the synthesis of brain histamine.