T. Biegański

Interference of aldehyde metabolizing enzymes with diamine oxidase/histaminase/activity as determined by 14C putrescine method.

Abstract The Δ 1 pyrroline formation, as an indicator of diamine oxidase activity according to Okuyama and Kobayashi 14 C putrescine test [1], has been investigated in several tissue homogenates. When guinea pig liver homogenate was used as a source of enzyme in the presence of aldehyde dehydrogenase inhibitors chloral hydrate and acetaldehyde the level of formation Δ 1 pyrroline was strongly increased in a dose-dependent manner. Also inhibition of aldehyde reductase by phenobarbital enhanced Δ 1 pyrroline formation, but to a lesser degree. In other tissues, with very high initial diamine oxidase activity (rat intestine, dog kidney) or with very low diamine oxidase activity (guinea pig skin, dog liver) the influence of these inhibitors was only slight. Pyrazole, an inhibitor of alcohol dehydrogenase exerted only a small effect on Δ 1 pyrroline formation. All aldehyde-metabolizing enzymes inhibitors, except pyrazole, were without effect on purified pea seedling and hog kidney diamine oxidases. The use of aldehyde-metabolizing enzymes inhibitors may help to reveal the real values of diamine oxidase activity, when tissues homogenates are used as a source of enzyme.

Human intestinal diamine oxidase: Substrate specificity and comparative inhibitor study

For an 80-fold purified preparation of human intestinal diamine oxidase the optimum conditions of incubation, the substrate and the inhibitor specificity were tested. Putrescine was the most favoured substrate butNτ-methylhistamine and 2-methylhistamine were metabolized at optimum conditions with nearly the same velocity. Histamine reached about 50% of the reaction velocity of putrescine.Aminoguanidine and semicarbazide inhibited the human intestinal enzyme like a classical diamine oxidase. However, a distinct inhibition of human intestinal and pea seedling diamine oxidase was observed in presence of β-aminopropionitrile (weak inhibition of the human enzyme, strong inhibition of pea seedling diamine oxidase) and burimamide (strong inhibition of human intestinal enzyme, nearly no influence on pea seedling diamine oxidase).It is proposed to differentiate on the basis of functional considerations diamine oxidases with more histamine detoxicating activities from those being more involved in regulating polyamine levels in growing tissues.

Involvement of diamine oxidase in catabolism of14C-putrescine in micein vivo with special reference to the formation ofγ-aminobutyric acid

Tissues of mice killed 2.5 or 30 min after injection of14C-putrescine, contained14C-γ-aminobutyric acid, an unidentified14C-compound, and unchanged14C-putrescine. In mice pretreated with aminoguanidine, a powerful inhibitor of diamine oxidase, and then with14C-putrescine, tissue levels of the radioactive catabolites,γ-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.

Determination of histaminase (diamine oxidase) activity byo-dianisidine test: Interference of ceruloplasmin

Until nowo-dianisidine was used as an indicator substance in a test system for the determination of diamine oxidase. More recently, however, this substance was also used to measure ceruloplasmin activity. A study of the test principles revealed thato-dianisidine was the one denominator for both enzymes. As it was found for diamine oxidase the indicator was oxidized via peroxidase mediated H2O2 cleavage. Ceruloplasmin, however, oxidizedo-dianisidine directly with resulting free radical formation.An addition of histamine dihydrochloride or putrescine dihydrochloride to an incubation mixture, containing ceruloplasmin as enzyme ando-dianisidine orp-phenylene-diamine as substrates, produced an activation of the enzyme, being more than 10-fold in the presence of 1×10−2M putrescine at pH 7.0. It was assumed that an allosteric effect of the dihydrochloride component might be responsible for this activation.When the activity of purified diamine oxidase was determined by theo-dianisidine test and by the isotope assay, a very good correlation between both methods was found. But, in a mixture of diamine oxidase and ceruloplasmin, no differentiation between the two enzymic activities by theo-dianisidine test was possible. This observation demonstrated an interference of ceruloplasmin when theo-dianisidine method was used for the determination of diamine oxidase activity.To apply our findings also in vivo the amine oxidase activity increasing in guinea-pig plasma during inflammation, was determined by theo-dianisidine test and by specific methods for some amine oxidases. Despite an enhanced oxidation of theo-dianisidine observed, only an increase of ceruloplasmin activity was found. It was concluded that ceruloplasmin had no ‘histaminase activity’ as has been assumed by other authors using theo-dianisidine test.

Inhibition of plant and mammalian diamine oxidase by substrate analogues

Imidazoles, aliphatic substrate analogues and the natural dipeptides, carnosine and anserine, were investigated as inhibitors of diamine oxidase from the pig kidney, human pregnancy plasma and pea seedlings. Imidazole, methyli-midazoles,N-acetylimidazole, histamine andNτ-methyl-histamine are relatively potent inhibitors of mammalian diamine oxidase showing no influence on plant enzymes. Anserine and carnosine are inhibitors of pig kidney and pea seedling enzymes.K1 values are 2 μM and 10 μM respectively. Investigated natural derivatives of putrescine and cadaverine have no influence on diamine oxidase of different origin.In conclusion, we present some evidence to suggest that mammalian diamine oxidase, despite a high reaction rate with putrescine, is better adapted to histamine oxidation, whereas for plant enzymes the diamines are preferred substrates.

Diamine oxidase activity and imidazoleacetic acid formation in the foetal and maternal guinea pig liver

Diamine oxidase activity and imidazoleacetic acid formation in the foetal and maternal guinea pig liver during gestation were examined. DAO activity and IMAA formation in the foetal liver increased continuously, while maternal enzyme activity and ImAA formation in the second half of pregnancy simultaneously decreased. The roles of GABA and ImAA are discussed.

The histaminase activity of guinea-pig's plasma during experimental inflammation I. The enzyme activity

The plasma histaminase activity in guinea-pigs was found to increase by experimental inflammation induced by a subcutaneous turpentine injection and carrageenan peritonitis. The histaminase activity was raised 24 hours after the injection and did not return to normal values before 2 weeks. It was also observed that the alteration in the erythrocytes sedimentation rate followed a similar time course as that of the plasma level of histaminase. No relationship existed between the increased histaminase activity and skin oedema or changes in body temperature. The kinetics of the increase of plasma histaminase activity during inflammation are discussed.

Gamma-aminobutyric acid (GABA) formation from putrescine in guinea-pig liver during ontogenesis☆

1. The changes in hepatic diamine oxidase (DAO) activity of the foetal and maternal origin and their relations to GABA formation during pregnancy in guinea-pigs are described. 2. Foetal DAO activity continuously increased while the maternal enzyme from the 45th day of gestation onwards decreased. 3. Conversion of putrescine to GABA via oxidative deamination has been detected in the earliest studied day i.e. the 34th.

The histaminase activity of guinea-pig's plasma during experimental inflammation II. Some properties of the enzyme

The histamine inactivating enzyme(s) in guinea-pigs plasma, which increased during inflammation, has been studied in animals with inflammation produced by subcutaneous injection of turpentine. The enzyme was found to have a pH optimum between 6.2 and 6.5, and to have a slightly higher specificity for histamine than putrescine. It was also found that the histamine content of the plasma and liver reached a maximum at 24 hours, while the enzyme activity reached a maximum at 72 hours after experimental inflammation. The putrescine levels were not altered. It was also found that the animals with inflammation were less sensitive to histamine than the control animals.Additional studies in animals with liver damage produced by intraperitoneal injection of carbon tetrachloride suggested that the source of this increased plasma histaminedestroying activity was the liver.

Causal relationship between a tumour growth and the changes in histamine metabolism in tissues of sarcoma-bearing rat

The relationship between malignancy and histamine metabolism in the liver and the small intestine has been examined in sarcoma-bearing Wistar rats two weeks after subcutaneous implantation of a transplantable methylcholanthrene sarcoma Sa1828 and on the 3, 7 and 14th days after tumour extirpation. Two weeks after tumour implantation, the histamine level was increased by 100% and 50% in the liver and the small intestine, respectively. On the 3rd day after extirpation of the tumour the level of histamine had returned to the control values and remained unchanged during the next 10 days. Neither of the histamine catabolizing enzymes, diamine oxidase with a putrescine as a substrate or histamine methyltransferase were influenced by the existing tumour or by its extirpation except on the 14th day where a high increase in diamine oxidase activity was found. Some changes in the distribution of histamine metabolites suggest an involvement of an oxidative pathway of histamine catabolism as well as the aldehyde catabolizing enzymes in tumour development.