Comparison of histidine decarboxylases from rat stomach and brain with that from whole bodies of rat fetus

Abstract

Histidine decarboxylases from the stomach and brain of adult rats were purified 380- and 160-fold, respectively, and their properties compared with those of the enzyme from whole bodies of fetal rats (7600-fold purification). The molecular weights (about 90,000) and the apparent Km values for L-histidine (3 X 10(-4) M) of the three enzymes were similar. The pI value of the fetal enzyme was 5.0, and that of the brain enzyme was 5.4. Histidine decarboxylase of the stomach showed two peaks of activity corresponding to those of the fetal and brain enzymes (pI's of 5.0 and 5.4) on isoelectric focusing. Anti-fetal-histidine decarboxylase antiserum inhibited the stomach and fetal enzymes extensively, but the brain enzyme only slightly. These results indicate that there are at least two types of histidine decarboxylase in rat tissue.

Long-term depletion of histamine in guinea-pigs by administration of α-fluoromethylhistidine, a specific inhibitor of histidine decarboxylase; effect on the sensitivity of histamine receptors

“…with 100 mg/kg of a-FMH twice a day for 6 weeks. The HDC activities of tissues of guinea-pigs were in general lower than those of other animals; for instance, the HDC activity of the stomach was only one-sixtieth of that of rats [35]. But a-FMH-treatment decreased the activities in all the tissues to one-third to one-quarter of those of controls.…”