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A number of infants with an autosomal recessive form of combined immunodeficiency disease also lack adenosine deaminase (adenosine aminohydrolase; EC 3.5.4.4) activity in their erythrocytes. Other tissues from these infants contain only a few percent of the adenosine-deaminating activity present in corresponding normal tissue. The residual adenosine-deaminating activity in extracts from the spleen of a combined immunodeficient, adenosine deaminase-deficient patient was compared with adenosine deaminase from normal spleen. Affinity and immunoadsorbant column chromatography revealed distinct differences between the adenosine-deaminating activity in the patient's spleen and adenosine deaminase from normal spleen. The point of maximum activity and general configuration of the pH optimum curves were also different. erythro-9-(2-Hydroxyl-3-nonyl)adenine, a potent inhibitor of adenosine deaminase from normal spleen, had relatively little effect on the activity from the patient's spleen. In contrast, adenine was a better inhibitor of the activity in the patient's spleen than it was of the enzyme from normal tissue. An adenosine-deaminating activity with the same characteristics and specific activity as that in the patient's spleen was also isolated from normal spleen. These results suggest that the adenosine-deaminating activity in the spleen of this patient is not due to a mutant form of adenosine deaminase.
Stimulation of lipid peroxidation /increase in content of conjugated dienes and of malone dialdehyde/, which was prevented by administration of isoniazid or sodium thiosulphate, was detected in mitochondrial fraction of liver tissue obtained from rats with tuberculosis of lungs. At the same time, in the mitochondrial fraction a significant decrease in tyramine and serotonin deamination rates and an increase in histamine, lysine and putrescine deamination rates were observed. The altered ratio of the deamination rates of the nitrogenous compounds may be prevented by administration of isoniazid and sodium thiosulphate into the animals. A hypothesis is discussed on the possible significance of qualitative alteration /transformation/ in catalytic properties of the mitochondrial monoamine oxidase induced by the stimulation of lipid peroxidation as a cause underlying the reversible impairments in ratios of rates of the nitrogenous compounds deamination in tuberculosis.
The ability of the gut to inactivate various amines by oxidative deamination was tested with a 130-fold purified amine oxidase preparation from dog small intestine. Of 34 amines tested, putrescine, benzylamine, cadaverine, and serotonin were the most favourable substrates. Histamine was inactivated rapidly by this enzyme preparation, too. Histamine derivatives methylated at the imidazole nucleus were also deaminated, whereas Nalpha-methylhistamine was only a poor substrate and Nalpha, Nalpha-dimethylhistamine was not a substrate at all. Using a second procedure for the purification of amine oxidases from gut, the separation of a soluble monoamine oxidase from diamine oxidase was achieved by gel filtration on Sephadex G-200. The diamine oxidase deaminated putrescine (Km = 1.3 x 10(-4)M) and histamine (Km = 6.6 x 10(-5)M), but not serotonin, and was inhibited by aminoguanidine, but not by pargyline. The soluble monoamine oxidase inactivated serotonin (Km = 4.5 x 10(-4)M), but not histamine and putrescine and was inhibited by pargyline, but not by aminoguanidine. It was concluded that in dog small intestine (as well as in rabbit small intestine) only diamine oxidase was capable of inactivating histamine by oxidative deamination.
APOBEC3 family proteins are critical host factors that counteract and prevent the replication of retroviruses and other viruses through cytidine deamination. Human APOBEC3 proteins inactivate HIV-1 through the introduction of lethal mutations to viral genomes. In contrast, mouse APOBEC3 does not induce DNA hypermutation of murine retroviruses, although it retains functional cytidine deaminase activity. Why mouse APOBEC3 does not effectively deaminate murine retroviruses is still unknown. In this study, we found that the dead box helicase DHX15 interacts with mouse APOBEC3 and inhibits its deamination activity. DHX15 was packaged into murine leukemia virus (MLV) virions independent of its binding with APOBEC3. Moreover, DHX15 knockdown inhibited MLV replication and resulted in more G-to-A mutations in proviral DNA. Finally, DHX15 knockdown induced DNA damage in murine cells, suggesting that it plays a role in preserving genome integrity in cells expressing mouse APOBEC3 protein.
Thialysine is oxidatively deaminated by snake venom L-aminoacid oxidase at alkaline pH. The oxygen consumption curves show a characteristic diphasic course: the quick uptake of half a mole of oxygen per mole of substrate, in aggreement with a typical oxidative deamination, is followed by a slow extra oxygen consumption. The first product of the reaction is the corresponding alpha-oxo-epsilon-amino acid, which spontaneously cyclizes to the internal Schiff base 5-6-dihydro-delta 3,1,4-thiazin-3-carboxylic acid (TZCA). This latter has been identified by its UV absorption spectrum, by some chemical reactions, by paper chromatography, and by the production of cystamine and glyoxylic acid after prolonged oxidation of thialysine followed by acid hydrolysis. The possibility of an alpha-beta elimination reaction giving rise to cysteamine from thialysine, coupled to the oxidative deamination, has been excluded.
Statistically significant inhibition of oxidative deamination of several biogenic amines was found in mitochondrial fraction of heart muscle from rabbits and rats with experimental atherosclerosis and hypercholesterolemia, caused by various methods. Sensitivity of oxidative deamination of tryptamine to inhibitory effect of clorgyline (selective inhibitor of mitochondrial monoamine oxidases) was unaltered in rats with experimental hypercholesterolemia. The rate of oxidative deamination of beta-phenyl ethylamine, tryptamine, benzylamine as well as histamine and putrescine was inhibited after treatment of the mitochondrial fragments from healthy rabbit and rat heart muscles with preparations of oxidized linoleic and linolenic acids, concentration of which was increased in tissues under conditions of atherosclerosis.
The reductive deamination of guanylate to inosinate was demonstrable but occurred at low rates in human and rabbit erythrocytes incubated in vitro with or without glucose. However, the process was considerably accelerated in erythrocytes incubated with deoxyglucose. In human erythrocytes incubated with deoxyglucose, deamination was the major pathway of catabolism of guanylate; little or no guanylate was dephosphorylated. In rabbit erythrocytes, guanylate was both deaminated and dephosphorylated. Inosinate formed from guanylate was metabolized only by dephosphorylation in human erythrocytes, but in rabbit erythrocytes, it was also converted to xanthylate.
In the isolated rat vas deferens, various 2-substituted adenosine derivatives and adenosine inhibited contractions elicited by field stimulation but had little effect on responses to exogenous noradrenaline. 2-Chloroadenosine, 2-bromoadenosine, 2-hydroxyadenosine and 2-fluoroadenosine were all more potent than adenosine. Theophylline antagonized the action of the 2-substituted derivatives. The inhibitory action of adenosine was potentiated by dipyridamole, 2-amino-6-[(2-hydroxy-5-nitro)benzylthio]-9-beta-D-ribofuranosylpurine (HNBTG) or 2'-deoxycoformycin while that of 2-choloroadenosine was not altered by any of these drugs or by phenoxybenzamine, atropine or indomethacin. Pretreatment of the vas deferens with both HNBTG and 2'-deoxycoformycin eliminated the difference in inhibitory potency between adenosine and 2-chloroadenosine. These results indicate that 2-substituted adenosine derivatives, like adenosine, produce inhibition of transmission by acting on a presynaptic site which can be blocked by theophylline. The high apparent potency of 2-chloroadenosine compared to adenosine appears to be due to the former being neither taken up nor deaminated, while the apparent potency of adenosine is masked by uptake and deamination in this tissue.
The effect of age and thyroid hormones upon the ability of chick heart homogenates to metabolize monoamines has been investigated. 5-Hydroxytryptamine is entirely metabolized by a monoamine oxidase (MAO) with the characteristics of MAO-A, whereas some of the tyramine and all of the benzylamine are oxidatively deaminated by a clorgyline-resistant, but semicarbazide-sensitive enzyme, with a similar subcellular distribution to that of MAO. The remainder of the tyramine deamination is brought about by MAO-A and MAO-B. The specific activities of both clorgyline-sensitive and resistant enzymes are increased by the same proportion by increase in age or by treatment with (--)-thyroxine, and decreased by 2-thiouracil. The significance of these results is discussed.
Rates of oxidative deamination of polyamines were studied in rapidly growing hepatomas G-22 and G-27, in slowly growing hepatomas G-60, G-61, G-48, G-46 as well as in liver tissue of tumor-bearing animals and animals treated with nitrose piperidine. Diamine oxidase activity was not found in rapidly growing hepatomas. Treatment with pyridoxal-phosphate did not restore the diamine oxidase activity in hepatomas G-27, but distinctly increased the latter in the liver tissue of the tumor-bearing animals up to the level of the enzymatic activity found in liver tissue of the intact animals. On the contrary, high concentrations of pyridoxal-phosphate (above 0.02 mg) inhibited the diamine oxidase activity in liver tissue of the impaired and intact animals. The enzymatic activity was markedly decreased in slowly growing hepatomas G-60, G-61, G-48 and G-46 as compared with the activity in liver tissue of tumor-bearing animals. Oxidation of all the substrates used could be measured using hepatoma G-60, putrescine and spermidine - for hepatoma G-61, but only putrescine - for hepatoma G-48. No of the substrates used was deaminated by hepatoma G-46. Four-fold decrease in the diamine oxidase activity was observed during malignization of liver cells induced by nitrose piperidine. The diamine oxidase was mainly localized in the postmitochondrial fraction of hepatocytes.
Oxidative deamination of the epsilon-amino group of lysyl residues to form allysine is the initial reaction in the cross-linking of collagen and elastin in vertebrates. The allysyl residues, generated by lysyl oxidase in this reaction, condense with either other allysyl residues or epsilon-amino groups of lysyl or hydroxylysyl to form aldol or Schiff base cross-links. This paper presents evidence that similar allysyl residues and Schiff base cross-links are synthesized in cell envelopes of Escherichia coli. Acid hydrolysis followed by amino acid analysis of envelopes either reduced with NaB[3H]4 or labeled with [14C]lysine and reduced with NaBH4 yielded allysine and two labeled fragments with elution profiles and molecular weights (250 and 330) consistent with Schiff base products derived at least in part from allysine. When [6-3H]lysine-labeled cell envelopes were incubated at 37 degrees C, gradual release of tritiated water occurred. This suggests that an enzymatic reaction catalyzes the deamination of lysine in E. coli membranes and that the higher molecular weight proteins detected in stationary phase or in log phase cell envelopes after NaBH4 reduction occur as a result of formation of Schiff base cross-links.
Deamination of AMP in skeletal muscle sarcoplasmic reticulum followed by an increase in pH from 6,5 up to 8,0 leads in a liberation of part of Ca2+ from the SR vesicles. This effect is enhanced by K+, which activate the deamination, and is suppressed by Mg2+, which inhibit the reaction. The activating effect of AMP on Ca2+ efflux from the vesicles markedly decreases after AMP deaminase dissociation from the vesicles and is restored after reconstitution of their deaminase activity. Substitution of IMP for AMP causes a decrease of Ca2+ efflux from the vesicles. The data obtained are in good agreement with the assumption that the ammonium formation from AMP can favour the release of Ca2+ from some vesicles of SR.
The possible chemical mechanisms by which neutral solutions of sodium hypochlorite containing a high concentration of sodium chloride abolish the acidophilia of proteins in sections of fixed tissue are reviewed. The most probable one is the chlorination of the protein terminal amino groups, followed by the breakdown of the N-chloramine so formed into alpha-ketocarboxylic acid, nitrile or aldehyde groups. Hypochlorite solutions certainly do not deaminate tissue sections as was previously thought. Experimental evidence for the formation of relatively stable N-chloramine groups in situ and their limited conversion to aldehydes is reported. For example, the acidophilia of hypochlorite-treated sections was found to be restored after flooding them with hydriodic acid followed by the extraction of the liberated iodine with an alcohol. The significance of these experimental findings is discussed.
epsilon-N-acetylthialysine and epsilon-N-acetylselenalysine are oxidatively deaminated by Crotalus adamanteus l-aminoacid oxidase, giving rise to the corresponding alpha-ketoacids, identified by some chemical and chromatographic tests and by comparison with synthetic compounds. no cleavage of the C-S or C-Se bonds of the substrates occurs during the reaction. The enzyme acts as well on the epsilon-N-acetylderivatives of thialysine and selenalysine as on epsilon-N-acetyllysine. The substitution of the gamma methylene group of lysine by a sulfur or a selenium atom seems not to greatly affect the substrate specificity of the enzyme.
beta-methyl-aspartic acid is a substrate for beef kidney D-aspartate oxidase. The first product of a typical oxidative deamination, undergoes further spontaneous process of decarboxylation which gives as product, the alpha-keto-butyric acid.
Uracil-DNA glycosylase, which acts specifically on uracil-containing DNA, was purified 250-fold from an extract of Escherichia coli 1100. The enzyme releases free uracil from DNA, producing alkali-labile apyrimidinic sites in the DNA. The enzyme is active on both native and heat-denatured DNA of phage PBS1, which contains uracil in place of thymine. piX174 DNA which had been treated with bisulfite and then at alkaline pH was susceptible to the action of uracil-DNA glycosylase. Since DNA treated with bisulfite alone was less susceptible to the enzyme, it is likely that the enzyme recognizes deaminated cytosine, namely uracil, but not bisulfite adducts of uracil and cytosine in the treated DNA. DNA treated with nitrite or hydroxylamine was not attacked by the enzyme. Enzyme activity acting on bisulfite-treated DNA was absent from an extract of E. coli mutant BD10 (ung). The mutant exhibited higher sensitivity to bisulfite than did the wild-type strain and was unable to reactivate phage T1 pre-exposed to bisulfite and weak alkali.
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