scholarly journals The reaction of ornithine aminotransferase with ornithine

1982 ◽  
Vol 201 (1) ◽  
pp. 221-225 ◽  
Author(s):  
J A Williams ◽  
G Bridge ◽  
L J Fowler ◽  
R A John
Keyword(s):  
Amino Acids ◽  
Carbon Atom ◽  
Rat Liver ◽  
Dissociation Constants ◽  
Amino Group ◽  
Ornithine Aminotransferase ◽  
Mammalian Enzyme ◽  
Kinetics Of ◽  
Plant Enzyme

Rat liver ornithine aminotransferase is found to exchange the pro-S hydrogen on the delta-carbon atom of ornithine exclusively, thus showing that the mammalian enzyme transfers the delta-amino group and not the alpha-amino group as has been demonstrated with the plant enzyme [Mestichelli, Gupta & Spenser (1979) J. Biol. Chem. 254, 640-647]. The enzyme also transfers the alpha-amino group of glutamate and the kinetics of the half reactions between the enzyme and both amino acids are compared. Rate and dissociation constants for both reactions are determined.

Transamination of Ring-Substituted L-Phenylalanines by an Extract from Rat Liver Mitochondria

1973 ◽  
Vol 51 (4) ◽  
pp. 407-411 ◽  
Author(s):  
J. H. Tong ◽  
B. A. Stoochnoff ◽  
A. D'Iorio ◽  
N. Leo Benoiton
Keyword(s):  
Amino Acids ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Tyrosine Aminotransferase ◽  
Rat Liver Mitochondria ◽  
Amino Group ◽  
Mitochondrial Enzyme ◽  
Soluble Enzyme ◽  
Keto Acids ◽  
Mitochondrial Extract

The L- and D-isomers of m-tyrosine, o-tyrosine, p-chlorophenylalanine (p-CP), and p-fluorophenylalanine (p-FP) were tested as substrates for the soluble tyrosine aminotransferase and a mitochondrial extract of rat liver by measuring the amino acids formed with 2-oxoglutarate, oxaloacetate, and pyruvate as acceptors. None of the above were substrates for the soluble enzyme. L-m-Tyrosine, L-p-CP, and L-p-FP were transaminated at substantial rates (16–25% of the rate for L-tyrosine) by the mitochondrial enzyme with all three keto acids as amino group acceptors. A slow but definite transamination of L-o-tyrosine by the mitochondrial enzyme was demonstrated using labeled 2-oxoglutarate as acceptor.

Catabolism of arginine and ornithine in the perfused rat liver: effect of dietary protein and of glucagon

2000 ◽  
Vol 278 (3) ◽  
pp. E516-E521 ◽  
Author(s):  
Dan O'Sullivan ◽  
John T. Brosnan ◽  
Margaret E. Brosnan
Keyword(s):  
Amino Acids ◽  
Rat Liver ◽  
Dietary Protein ◽  
Reaction Pathway ◽  
Perfused Rat Liver ◽  
Ornithine Aminotransferase ◽  
Dibutyryl Camp ◽  
Similar Extent ◽  
Twofold Increase ◽  
Arginine Catabolism

The rates of oxidation of arginine and ornithine that occurred through a reaction pathway involving the enzyme ornithine aminotransferase (EC 2.6.1.13 ) were determined using14C-labeled amino acids in the isolated nonrecirculating perfused rat liver. At physiological concentrations of these amino acids, their catabolism is subject to chronic regulation by the level of protein consumed in the diet. 14CO2production from [U-14C]ornithine (0.1 mM) and from [U-14C]arginine (0.2 mM) was increased about fourfold in livers from rats fed 60% casein diets for 3–4 days. The catabolism of arginine in the perfused rat liver, but not that of ornithine, is subject to acute regulation by glucagon (10− 7 M), which stimulated arginine catabolism by ∼40%. Dibutyryl cAMP (0.1 mM) activated arginine catabolism to a similar extent. In retrograde perfusions, glucagon caused a twofold increase in the rate of arginine catabolism, suggesting an effect of glucagon on arginase in the perivenous cells.

scholarly journals The reaction of 2,4,6-trinitrobenzenesulphonic acid with amino acids, peptides and proteins

1968 ◽  
Vol 108 (3) ◽  
pp. 383-391 ◽  
Author(s):  
R. B. Freedman ◽  
G. K. Radda
Keyword(s):  
Amino Acids ◽  
Glutamate Dehydrogenase ◽  
Free Amino ◽  
Reactive Species ◽  
Second Order ◽  
Amino Group ◽  
Exponential Rate ◽  
Amino Groups ◽  
Sh Group ◽  
Kinetics Of

1. The kinetics of the reaction of 2,4,6-trinitrobenzenesulphonic acid with various amino acids, peptides and proteins were studied by spectrophotometry. 2. The reaction of the α- and ∈-amino groups in simple amino acids was found to be second-order, and the unprotonated amino group was shown to be the reactive species. 3. By allowing for the concentration of unreactive −NH3+ group, intrinsic reactivities for the free amino groups were derived and shown to be correlated with the basicities. 4. The SH group of N-acetylcysteine was found to be more reactive to 2,4,6-trinitrobenzenesulphonic acid than most amino groups. 5. The reactions of insulin, chymotrypsinogen and ribonuclease with 2,4,6-trinitrobenzenesulphonic acid were analysed in terms of three exponential rate curves, each referring to one or more amino groups of the proteins. 6. The reaction of lysozyme with 2,4,6-trinitrobenzenesulphonic acid was found to display an acceleration effect. 7. From the reaction of 2,4,6-trinitrobenzenesulphonic acid with glutamate dehydrogenase at several enzyme concentrations, it was possible to discern two sets of amino groups of different reactivity, and to show that the number of groups in each set was decreased by aggregation of the enzyme.

scholarly journals Studies of the specificity and kinetics of rat liver spermidine/spermine N1-acetyltransferase

1983 ◽  
Vol 213 (3) ◽  
pp. 701-706 ◽  
Author(s):  
F Della Ragione ◽  
A E Pegg
Keyword(s):  
Rat Liver ◽  
Kinetic Mechanism ◽  
Competitive Inhibitor ◽  
Aliphatic Chain ◽  
Amino Group ◽  
Acetyl Coa ◽  
Competitive Kinetics ◽  
Primary Amino ◽  
Secondary Amino ◽  
Kinetics Of

The substrate specificity and kinetic mechanism of spermidine N1-acetyltransferase from rat liver was investigated using a highly purified (18 000-fold) preparation from the livers of rats in which the enzyme was induced by treatment with carbon tetrachloride (1.5 ml/kg body wt. 6h before death). The enzyme catalysed the acetylation of spermidine, spermine, sym-norspermidine, sym-norspermine, N-(3-aminopropyl)-cadaverine, N1-acetylspermine, 3,3′-diamino-N-methyldipropylamine and 1,3-diaminopropane, but was inactive with putrescine, cadaverine, sym-homospermidine and N1-acetylspermidine. These results suggest that the enzyme is highly specific for the acetylation of a primary amino group that is separated by a three-carbon aliphatic chain from another nitrogen atom (i.e. the substrates are of the type H2N[CH2]3NHR). The maximal rates of acetylation of 1,3-diaminopropane and 3,3′-diamino-N-methyldipropylamine were much lower than the maximal rates with spermidine or sym-norspermidine as substrates, suggesting a preference for a secondary amino group bearing the aminopropyl group that is acetylated. The best substrates for acetylation were sym-norspermidine and sym-norspermine, which had Km values of about 10 micrograms and Vmax. values of about 2 mumol of product/min per mg of enzyme compared with Km of 130 microM and Vmax. of 1.3 mumol/min per mg for spermidine. N1-Acetylspermidine (the product of the reaction) and N8-acetylspermidine were weak inhibitors and were competitive with spermidine, having Ki values of about 6.6 mM and 0.4 mM respectively. N1-Acetylspermidine was a non-competitive inhibitor with respect to acetyl-CoA. CoA was also inhibitory to the reaction, showing non-competitive kinetics when either [acetyl-CoA] or [spermidine] was varied. These results suggest that the reaction occurs via an ordered Bi Bi mechanism in which spermidine binds first and N1-acetyl-spermidine is the final product to be released.

The Reaction of Aminoacylase with Chloromethylketone Analogs of Amino Acids

1977 ◽  
Vol 32 (9-10) ◽  
pp. 769-776 ◽  
Author(s):  
Jürgen Frey ◽  
Werner Kordel ◽  
Friedhelm Schneider
Keyword(s):  
Amino Acids ◽  
Aspartic Acid ◽  
Active Site ◽  
Lysine Residue ◽  
Amino Group ◽  
Sh Groups ◽  
Competitive Inhibitors ◽  
Kinetics Of ◽  
Covalently Bound

Abstract1. Aminoacylase is irreversibly inactivated by the chloromethylketone analogs of benzyloxy-carbonyl-L-alanine, L-alanine, L-leucine, L-aspartic acid (β), tosyl-L-phenylalanine and L-leucyl-L-alanine. The kinetics of the inactivation of the enzyme by the halo-methylketones were investigated.2. Leucyl-and alanyl chloromethylketone inactivate the enzyme by blocking of 4 SH groups. Experiments with [U-14C] leucyl chloromethylketone confirm that maximal 4 residues are covalently bound to the protein.3. Inactivation of the enzyme by benzyloxycarbonylalanyl and tosylphenylalanyl chloromethyl­ ketone is the result of the substitution of the £-amino group of one lysine residue per active site and not of SH groups. However, in the presence of competitive inhibitors these halomethylketones react only with the SH groups of the enzyme, too.

Effect of Amino Group Charge on the Photooxidation Kinetics of Aromatic Amino Acids

2013 ◽  
Vol 118 (2) ◽  
pp. 339-349 ◽  
Author(s):  
Natalya N. Saprygina ◽  
Olga B. Morozova ◽  
Günter Grampp ◽  
Alexandra V. Yurkovskaya
Keyword(s):  
Amino Acids ◽  
Aromatic Amino Acids ◽  
Amino Group ◽  
Kinetics Of

scholarly journals Hepatic zonation of the catabolism of arginine and ornithine in the perfused rat liver

1998 ◽  
Vol 330 (2) ◽  
pp. 627-632 ◽  
Author(s):  
Dan O'SULLIVAN ◽  
T. John BROSNAN ◽  
E. Margaret BROSNAN
Keyword(s):  
Amino Acids ◽  
Rat Liver ◽  
Hepatic Vein ◽  
Small Population ◽  
Arginase Activity ◽  
Perfused Rat Liver ◽  
Ornithine Aminotransferase ◽  
Arginine Catabolism ◽  
14Co2 Production

The metabolism of 14C-labelled arginine and ornithine was studied in the isolated, nonrecirculating, perfused rat liver. The catabolism of these amino acids required ornithine aminotransferase since treatment of rats with gabaculine, an inhibitor of this enzyme, decreased substantially the production of 14CO2 from the 14C-labelled amino acids. In the liver, ornithine aminotransferase is restricted to a small population of hepatocytes proximal to the terminal hepatic vein [Kuo, F. C., Hwu, W. L., Valle, D. and Darnell Jr., J. E. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 9468-9472], i.e. the perivenous subpopulation of hepatocytes. Catabolism of arginine requires arginase to convert arginine to ornithine which can then be catabolized through ornithine aminotransferase. The presence of arginase activity in the perivenous hepatocytes was demonstrated by experiments in which livers were perfused with [14C]arginine in both antegrade and retrograde directions. Identical rates of 14CO2 production were obtained in these experiments, a result which could only occur if the process of arginine catabolism through ornithine aminotransferase can be carried out in its entirety in the perivenous cells.

scholarly journals Dissociation constants and structures of zwitterions

1937 ◽  
Vol 158 (893) ◽  
pp. 68-96 ◽  
Keyword(s):  
Amino Acids ◽  
Carbon Atom ◽  
Dissociation Constant ◽  
Dissociation Constants ◽  
Carboxyl Group ◽  
Aliphatic Acid ◽  
Hydrogen Atoms ◽  
Positively Charged ◽  
Quantitative Treatment

Dissociation constants of amino-acids in relation to their structures have been discussed in recent years in several publications (Schmidt, et al ., 1929; Cohn, 1931; Greenstein, 1931; Melville and Richardson, 1935). A more quantitative treatment seems desirable, however, and such a treatment is attempted in this paper. If in the aliphatic acid R . CH 2 . COOH one of the hydrogen atoms attached to the α-carbon atom is replaced by the positively charged NH 3 + group the ionization of the carboxyl group is increased about 280-fold. If substitution occurs in the β- or γ -positions the dissociation constant increases only about 12- or 5-fold respectively.

The kinetics of combination of carbon dioxide with the anions of glycine, glycyl-glycine, and related amino acids

1966 ◽  
Vol 164 (996) ◽  
pp. 401-410 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Amino Acids ◽  
Acetic Acid ◽  
Caproic Acid ◽  
Thermal Method ◽  
Amino Group ◽  
Phenyl Acetic Acid ◽  
Kinetics Of ◽  
Phenyl Alanine ◽  
Glycyl Glycine

The velocity constants k ' of the reaction of carbon dioxide with the anions of the amino acids glycine, glycyl-glycine, α-alanine, β-alanine, valine, histidine, β-phenyl alanine, α-amino phenyl acetic acid, and e-amino caproic acid have been determined by the rapid thermal method. At 25 °C the value of k ' is given approximately by the equation log 10 k ' = 0.262 p K + 1.197 where p K is the p K value of the amino group which reacts. For glycine and glycyl-glycine the energies of activation have been determined as 8.2 and 8.3 kcal respectively over the range 10 to 40 °C.

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