Abstract
At least two enzymes may catalyze the mammalian biosynthesis of histamine: aromatic L-amino acid decarboxylase, also referred to as DOPA (3,4-dihydroxyphenylalanine) decarboxylase and “specific” histidine decarboxylase. High activities of the latter enzyme appear in the tissues of the fetal mouse a few days before term and disappear after delivery. The activity (per unit weight) of DOPA decarboxylase is low during prenatal development but increases markedly after parturation. When the DOPA decarboxylase activity is expressed per mg of protein a fairly constant value is obtained during fetal and neonatal development. Histidine decarboxylase appears in the kidney of the pregnant mouse shortly after mating: maximal activity develops a few days before parturition. The DOPA decarboxylase activity of the normal mouse kidney is high and is not affected by pregnancy. The properties of semi-purified preparations of histidine decarboxylase from the fetal mouse and from the kidney of the pregnant mouse are similar to those of fetal rat histidine decarboxylase and quite different from the nonspecific aromatic L-amino acid decarboxylase.
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