Kidney amine oxidases

Early studies performed with bovine plasma and porcine kidney amine oxidases have shown that the enzymes undergo irreversible inactivation upon reaction with several acetylenic substrates (propargylamine, 2-chloroallylamine and 2-butyne-1,4-diamine), which was diminished by substrate protection [118]. Other types of mechanism-based inactivators of bovine plasma amine oxidase are some glycine esters with relatively acidic a-protons. These esters are converted to ketenes, which may acylate the active site and inactivate the enzyme [119]. 

Pig kidney diamine oxidase was inhibited by CuSO (for 49 % at 0.1 mM) and by the Cu complexes of lysine and tyrosine, but not by (Cu,Zn)-SOD Similar observations were made with purified bovine plasma amine oxidase There was only a weak... 

That amines formed from naturally occurring amino acids are partly responsible for chronic hypertension is a rather attractive hypothesis first suggested by the experiments of Holtz (35). Besides the normal metabolic enzymes of amino acids, tissues, especially kidney, liver, and brain, contain amino acid decarboxylases, some of them specific for certain amino acids, some less so. These are anaerobic enzymes. After decarboxylation, certain monoamines are deaminated by amine oxidases which are sensitive to oxygen tension. The best known of these oxidases is the enzyme of Blaschko, Richter, and Schlossmann (9), which may be a mixture of three or more (29), and which is specific for many nonsubstituted vasoactive amines found in the body, with the notable exception of histamine. 

Tyrosinase and amine oxidase appear to be true antihypertensive substances they are useless at the present time for clinical application. Many cardiotoxic and depressor agents are known which will lower blood pressure at the expense of kidneys, heart, or blood volume. A few newer compounds, however, are now being studied which on preliminary trial appear to fit the definition of antihypertensive substances. It is believed that, in the not too distant future, a practical method for the control of this prevalent condition will be found. 

The major enzyme involved in the formation of ammonia in the liver, brain, muscle, and kidney is glutamate dehydrogenase, which catalyzes the reaction in which ammonia is condensed with 2-oxoglutarate to form glutamate (Sec. 15.1). Small amounts of ammonia are produced from important amine metabolites such as epinephrine, norepinephrine, and histamine via amine oxidase reactions. It is also produced in the degradation of purines and pyrimidines (Sec. 15.6) and in the small intestine from the hydrolysis of glutamine. The concentration of ammonia is regulated within narrow limits the upper limit of normal in the blood in humans is 70/tmol L-1. It is toxic to most cells at quite low concentrations hence there are specific chemical mechanisms for its removal. The reasons for ammonia toxicity are still not understood. The activity of the urea cycle in the liver maintains the concentration of ammonia in peripheral blood at 20/ molL. ... 

Even enantioselective oxidations of some alkyl-, benzyl-, or phenylethyl- (arylethyl-) amines were reported with diamine oxidase from pea settlings 141 f Porcine kidney diamine oxidase was used for the oxidative transformation of Nitraria alkaloids such as nazlinin 421. 

Diamine oxidase occurs, like amine oxidase, in bacteria, animals, and plants [133]. The comparison of amino acid sequences of the amiloride-binding protein from human kidney, rat colon, diamine oxidase from human placenta, pig kidney, and amine oxidase from Hansenula polymorpha and lentil seeds has shown that the amiloride-binding protein and diamine oxidase are identical proteins[29]. The amiloride-binding protein was previously postulated to function as an epithelial sodium-transporter. While its physiological function is still... 

Structure. Diamine oxidases are homo-dimeric enzymes. The subunits weigh between 60 and 105 kD depending upon the organism of origin [114]. Human diamine oxidase from kidneys is composed of 752 amino acid residues, and the corresponding enzyme from rat colon has 747 residues [29]. Diamine oxidases share the TOPA-chinon cofactor with amine oxidases. The ligands of the type 2 copper center in diamine oxidase are possibly the conserved residues Cys 391, Cys 417, and His 510 [29]. 

The results were further confirmed by resonance Raman spectrometry on comparing the spectra of phenylhydrazone and p-nitrophenylhydrazone of bovine plasma amine oxidase with the derivatized pentapeptides of the active site and the model compound. All these spectra showed great similarity in position (wavenumber) and spectral band intensity, while the spectrum of a PQQ model compound differed markedly [45]. Similar experiments confirmed the presence of topa quinone in porcine kidney, pea seedling and Arthrobacter PI amine oxidases. Moreover, the experimental data obtained for intact enzymes excluded the possibility of an artificial topa quinone formation during the proteolysis and peptide isolation [45]. 

Later, the presence of topa quinone was accordingly confirmed in the amine oxidases from porcine serum and kidney and pea seedling by resonance Raman spectrometry of active-site labeled peptides [48]. Comparison of amino acid sequences of these peptides with the sequences of those from bovine plasma and H. polymorpha amine oxidases demonstrated the presence of a consensus sequence Asp-TPQ-Asp/Glu as shown in Fig. (1). Using the pH-dependent shift of the absorption maximum of the enzyme p-nitrophenylhydrazone, which is considered to be a reliable indirect proof, the presence of topa quinone was also shown... 

Recently, the cofactor peptides have also been isolated from semicarbazide-sensitive amine oxidases purified from bovine and porcine aortas [52], sequenced and confirmed to contain the topa quinone. The same topa quinone consensus sequence was also found in the primary structures of amine oxidases from human kidney [53], human retina [54] and rat colon [55], so called amiloride-binding proteins , and amine oxidase from human placenta [56] that shows 81% identity with bovine plasma amine oxidase [57], bovine lung amine oxidase [58], and amine oxidases from pea and lentil seedlings [59,60], chick pea seedlings [61], and Arabidopsis thaliana [62] obtained by the molecular cloning of respective DNAs. 

Table 1. Alignment of amino acid sequences of several copper amine oxidase around the position of topa quinone. The sequences were obtained by translation the corresponding cDNAs except for the enzymes from porcine kidney and porcine serum and the benzylamine oxidase from Hansenula polymorpha where they were determined by automated Edman degradation of peptides. Homologous consensus sequence around the cofactor is underlined, the tyrosyl precursor of topa quinone is shown as y.

The above reaction mechanism has been confirmed by experimental studies. The stoichiometric formation of the aldehyde, H2O2, and ammonia from several substrates has been demonstrated with amine oxidases purified from beef plasma (ISl) and pea seedlings 1117,1S8), and with diamine oxidase purihed from hog kidney acetone powder 1 4)-... 

The kidney is an organ for both excretion and metabolism. It contains relatively high concentrations of amine oxidases and amino acid oxidases, i.e. enz5rmes involved in the production of free ammonia. This helps to explain the very high concentration of NH4+ ions in urine. The enzymes of oxidative metabolism (citrate cycle, respiratory chain) are also present— as in all cells. The kidney consumes relatively large proportions of oxygen and produces much ATP, which it needs for its excretionary activity. 

Yasukawa, K., Nakano, S., and Asano, Y, "Tailoring D-Amino acid oxidase from the pig kidney to R-stereoselective amine oxidase and its use in the deracemization of -methylbenzylamine." Angew. Chem. Int. Ed., 53, 4428-4431 (2014). 

Imino acids are easily decarboxylated (188) and the amine could then be set free either through hydrolysis or through displacement by a second molecule of amino acid. None of the amino acid decarboxylases has been prepared in pure form, but Werle and Heitzer (186) have purified histidine decarboxylase about 35-fold. Recently, pyridoxal phosphate was shown to be the prosthetic group of several amino acid decarboxylases (7,74,162). For optimal yields on amines, incubations with amino acid decarboxylases were carried out under anaerobic conditions (91) in order to prevent the action of amine oxidase, and, in rat kidneys, also that of Z-amino acid oxidase. 

Amine oxidase was found in a variety of tissues (13,20,87,185) the highest concentrations occurred in liver and kidney. The kidneys of rats, however, in contrast to those from man (19), ox, pig, and sheep, seem to contain almost no, or only relatively little, amine oxidase (20,87,92,144, 185). 

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