Aspects on diamine oxidase activity and its determination

Polyamines, folic acid supplementation and cancerogenesis

Clinical practice and experimental studies have shown the necessity of sufficient quantities of folic acid intake for normal embryogenesis and fetal development in the prevention of neural tube defects (NTDs) and neurological malformations. So, women of childbearing age must be sure to have an adequate folate intake periconceptionally, prior to and during pregnancy. Folic acid fortification of all enriched cereal grain product flour has been implemented in many countries. Thus, hundreds of thousands of people have been exposed to an increased intake of folic acid. Folate plays an essential role in the biosynthesis of methionine. Methionine is the principal aminopropyl donor required for polyamine biosynthesis, which is up-regulated in actively growing cells, including cancer cells. Folates are important in RNA and DNA synthesis, DNA stability and integrity. Clinical and epidemiological evidence links folate deficiency to DNA damage and cancer. On the other hand, long-term folate oversupplementation leads to adverse toxic effects, resulting in the appearance of malignancy. Considering the relationship of polyamines and rapidly proliferating tissues (especially cancers), there is a need for better investigation of the relationship between the ingestion of high amounts of folic acid in food supplementation and polyamine metabolism, related to malignant processes in the human body.

Participation of aldehyde dehydrogenase in the oxidative deamination pathway of histamine and putrescine

Some guinea pig tissue homogenates have shown the ability to catabolize, in vitro, imidazoloacetaldehyde (ImAAL) and gamma-aminobutyraldehyde (GABAL) via NAD-dependent aldehyde dehydrogenase (ALDH, EC 1.2.1.3). The liver, kidney, small intestine and gastric mucosa are the richest sources of ALDH activity towards ImAAL. The liver, kidney, small intestine and pancreas also show ALDH activity with GABAL as a substrate. All tissues tested have shown low Km and high Km ALDH activity with propionaldehyde as substrate. The guinea pig liver ALDH which is able to oxidize ImAAL and GABAL is located exclusively in the cytoplasm.

An improved spectrophotometric assay for histamine and diamine oxidase (DAO) activity

Diamine oxidase or its substrates can be measured using a coupled reaction with peroxidase and the chromogen 3-methyl-2-benzothiazolone hydrazone (MBTH) with an appropriate acceptor such as 3-(dimethylamino)benzoic acid (DMAB). This method provides a more rapid and sensitive method of measuring histamine than current colorimetric assays; using this system, histamine was quantitated at concentrations of 10 to 400 mumol/l. The Km of DAO was determined to be 2.9 X 10(-5) M, a lower value than previously reported.

In vitro metabolism of cadaverine in the pregnant rat

The in vitro metabolism of 14C-cadaverine by diamine oxidase was investigated in various tissues of pregnant and non-pregnant rats. The metabolites formed were: delta 1-piperideine, delta-aminovaleric acid, carbon dioxide and some unidentified compound(s). In most of the tissues investigated delta 1-piperideine was the predominant metabolite, but considerable amounts of delta-aminovaleric acid and the unidentified compound(s) were also formed. The oxidative products of cadaverine might be of importance in various physiological and pathophysiological connections associated with elevated diamine oxidase levels.

Involvement of diamine oxidase in catabolism of 14C-putrescine in mice in vivo with special reference to the formation of gamma-aminobutyric acid

Tissues of mice killed 2.5 or 30 min after injection of 14C-putrescine, contained 14C-gamma-aminobutyric acid, an unidentified 14C-compound, and unchanged 14C-putrescine. In mice pretreated with aminoguanidine, a powerful inhibitor of diamine oxidase, and then with 14C-putrescine, tissue levels of the radioactive catabolites, gamma-aminobutyric acid and the unidentified compound were markedly reduced. The data suggest that diamine oxidase is involved in the first step of putrescine metabolism and that intestine is the main site for this step. This and other aspects of putrescine metabolism are discussed.

Metabolism of putrescine in the pregnant rat

The in vivo metabolism of 14C-putrescine injected to rats before, during and after pregnancy was studied. Within 30 min of the administration of the isotope 9-12% of the injected radioactivity was recorded as 14CO2 in the expired air and after 5 h 60% was expired. The radioactivity excreted in the urine during the first day following the 14C-putrescine administration consisted of unmetabolized putrescine, gamma-aminobutyric acid (GABA) and some unidentified compound(s). No radioactive polyamines were detected in the urine. After treatment of pregnant rats with the diamine oxidase inhibitor aminoguanidine the expiration of 14CO2 was almost completely inhibited. In the urine increased amounts of unmetabolized putrescine were excreted while the excretion of GABA and the unidentified compound(s) were decreased. In addition 14C-spermidine appeared in the urine. The in vitro metabolism of putrescine was determined by the incubation of different tissues of pregnant and non-pregnant rats with 14C-putrescine. The 14C-metabolites derived via the diamine oxidase pathway (delta 1-pyrroline, GABA, some unidentified compound(s) and carbon dioxide) varied in magnitude with the tissue investigated. GABA was found to be a main metabolite of putrescine in several tissues of the pregnant rat. The content of putrescine and spermidine was elevated in several tissues as well as the blood on the 19th day of pregnancy in rats treated with aminoguanidine, while the content of spermine was unchanged.

Hog kidney diamine oxidase conversion of biogenic diamines to inhibitors of cell proliferation

Hog kidney diamine oxidase (DAO) interacted with 1,3-diaminopropane, putrescine and cadaverine to arrest proliferation of cultured mammalian cells. The byproducts of DAO-substrate interaction, H2O2 and NH4+ are themselves cytotoxic but were apparently not responsible for any significant antiproliferative effect in the experimental system. DAO is known to react with putrescine to generate labile 4-aminobutyraldehyde. This primary product was compatible with a compound (radio-labelled) separated from DAO-putrescine reactive mixtures by ion-exchange chromatography. Its rate of generation, level attained and lability (half-life, 2 hr) in culture simulated conditions were measured. Circumstantial evidence suggested that the amine aldehyde products of diamine oxidation had a potent antiproliferative effect on cells.

Inhibition of diamine oxidase by antimalarial drugs

The antimalarial drugs amodiaquine, quinacrine and chloroquine inhibit the catabolism of putrescine by the rat. Amodiaquine, the most potent of the three, does so in a dose-dependent fashion. This is attributed to the action in vivo of the drugs on diamine oxidase, an enzyme that is inhibited by them in vitro.

Diamine oxidase activity and gamma-aminobutyric acid formation in medullary carcinoma of the thyroid

The formation of different metabolites from 14C-putrescine via oxidative deamination has been studied in patients with medullary carcinoma of the thyroid (MCT) and in control subjects. The neoplastic tissue from MCT patients produced in addition to delta 1-pyrroline, large quantities of GABA and some unidentified compound(s), whereas the formation of these metabolites in normal thyroid tissue was almost negligible. Plasma from patients with MCT contained higher diamine oxidase activity than plasma from control subjects, but there was a considerable overlap between the two groups. Determination of the as yet unidentified compound(s) could possibly become a sensitive tool in the diagnosis and follow-up of carcinomas associated with a high diamine oxidase activity.

Formation of GABA via oxidative deamination of putrescine in ovaries of immature rats after gonadotrophin stimulation

The diamine oxidase catalyzed metabolism of 14C-putrescine was studied in the ovaries of immature rats with and without stimulation by gonadotrophin. This stimulation resulted in a statistically significant increase in the deamination rate of putrescine with a very predominant production of gamma-aminobutyric acid. No formation of polyamines was observed which indicated an importance of putrescine or of products of its oxidative deamination during this cellular activity.

In vitro metabolism of putrescine by diamine oxidase in tissues of the pregnant rat

The metabolism of 14C-putrescine by diamine oxidase was tested on the 19th day of pregnancy in different organs of rats. The highest turnover was found in maternal placenta and uterus where 94% of the reaction product was identified as delta 1-pyrroline. Considerable deamination rates were also observed in ovary, liver and fetal placenta where, however, gamma-aminobutyric acid was the predominant product. In the kidney only a small diamine oxidase activity was measured. No formation of spermidine or spermine from 14C-putrescine was detected.