Selective irreversible inhibition of mammalian histidine decarboxylase by alpha-chloromethyl histidine [proceedings]

The potential use of mechanism-based enzyme inactivators in medicine

Mechanism-based enzyme inactivator, alanine racemase, S-adenosylhomocysteine hydrolase, D-amino acid aminotransferase, gamma-aminobutyric acid aminotransferase, arginine decarboxylase, aromatase, L-aromatic amino acid decarboxylase, dihydrofolate reductase, dihydroorotate dehydrogenase DNA polymerase I, dopamine beta-hydroxylase, histidine decarboxylase, beta-lactamase, monoamine oxidase, ornithine decarboxylase, serine proteases, testosterone 5 alpha-reductase, thymidylate synthetase, xanthine oxidase.

Histidine decarboxylase inhibition: a novel approach towards the development of an effective and safe gastric anti-ulcer drug

The involvement of histamine in mediating gastric function under normal and pathological conditions has been largely established. The relationship between gastric acid production and peptic ulcer diathesis is also well known. Recently, endogenous histamine formation and its release from mast cells has been implicated in the pathogenesis of human and experimental gastric ulcers produced by restraint and pyloric ligation. It has also been implicated in the gastric mucosal damage produced by drugs like aspirin, phenylbutazone and reserpine. These observations suggest that histidine decarboxylase inhibitors may be useful in the prevention of such lesions. Our studies on the evaluation of some histidine decarboxylase inhibitors show that these compounds have a promising potential for developing an effective and safe anti-ulcer drug. This mini-review incorporates the results of our studies which have been adequately supported by other studies as well.

alpha-Fluoromethyl histidine. Inhibition of histidine decarboxylase in pylorus ligated rat

alpha-Fluoromethyl histidine is an irreversible inhibitor of histidine decarboxylase. The injection of a single dose to pyloric-ligated rats inhibits gastric mucosal histidine decarboxylase in a dose-dependent manner but does not modify histamine content and gastric acid secretion even at the highest dose used. Administration of cimetidine increases histidine decarboxylase activity, decreases histamine level in gastric mucosa and inhibits gastric acid secretion. The co-administration of alpha-fluoromethyl histidine blocks the augmentation in enzyme activity, maintains lowered histamine level and prolongs the antisecretory action of cimetidine.

Inhibition of histamine synthesis in brain by alpha-fluoromethylhistidine, a new irreversible inhibitor: in vitro and in vivo studies

alpha-Fluoromethylhistidine (alpha-FMH), a new potent inhibitor of histidine decarboxylase (HD), has been used for in vitro and in vivo studies of brain HD. Following a preincubation with (+)-alpha-FMH, brain HD activity was inhibited in a time-dependent and concentration-dependent manner. The enzyme activity was not restored by overnight dialysis against standard buffer. The (-) antimer of alpha-FMH was ineffective. When injected intraperitoneally in a single dose of 20 mg/kg, (+/-)-alpha-FMH induced a complete loss in HD activity in cerebral cortex and hypothalamus as well as in peripheral tissues, such as stomach. At a dosage of 100 mg/kg (+/-)-alpha-FMH did not alter histamine-N-methyltransferase, DOPA decarboxylase, and glutamate decarboxylase activities. The maximal decrease of HD activity occurred after 2 h in both cerebral cortex and hypothalamus, but the time course of the recovery of enzyme activity was slower in the cerebral cortex. The enzyme activity reached control value within 3 days in hypothalamus and was not fully restored after 4 days in cerebral cortex. Contrasting with the diminished HD activity, a substantial concentration of histamine remained present in five regions of mouse brain. Thus, alpha-FMH is a highly specific irreversible inhibitor of brain HD activity and its efficacy makes it useful to study the physiological role of brain histamine.