2- , arginase

Arginase is added to the reaction mixture to split the arginine formed by the lyase into ornithine and urea, which is determined. 

05 ml of a 1 10 liver homogenate in 0.1% CTAB is added 0.25 ml of substrate mixture. This contains 0.03 M KH2PO4 and 0.03 M K2HPO4, adjusted to pH 7.3 with K2HPO4, with 0.0035 M argininosuccinic acid and finally 2 mg of arginase per milliliter. The reaction mixture is incubated for 30 minutes at 37°C, and 0.05-ml samples are removed into 0.1-ral of 7% perchloric acid at 0, 5, 10, 15, and 30 minutes. 

After centrifugation, the urea is estimated in the supernatant by the method of Kulhanek and Vojtiskova (K13). A blank and standards containing 1, 2, and 4 mg/100 ml urea are treated in the same way. 

The urea formed from arginine by the action of this enzyme is directly 

Provided the tubes of deproteinizing solution are prepared in advance of the biopsy, then the reaction mixtures, and last the homogenates, it is possible to measure all 5 enzymes, including ornithine transcarbamylase at two different pH s, in a tissue specimen in 1 hour. The homogenates are kept in ice until they are used, and the last incubation is begun about 30 minutes after the homogenates are made. At least 50 mg of liver is required. 

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Argentite [1332-04-3] Argentodi thiosulfate Argentotri thiosulfate Arginase... 

Mn-+ K+ Ni " Arginase Pyruvate kinase (also requires Mg ) U rease Tetrahydrofolate (THF) Other one-carbon groups Thymidylate synthase... 

L-Arginine Arginase + Urease (double reaction) nh3, co2 Tris pH 7 NHj-airgap ... 

Hyperargininemia. This defect is characterized by elevated blood and cerebrospinal fluid arginine levels, low erythrocyte levels of arginase (reaction 5, Figure 29-9), and a urinary amino acid pattern resembling that of lysine-cystinuria. This pattern may reflect competition by arginine with lysine and cystine for reabsorption in the renal tubule. A low-protein diet lowers plasma ammonia levels and abolishes lysine-cystinuria. 

Iyer R et al The human arginases and arginase deficiency. J Inherit Metab Dis 1998 21 86. 

Arginase, activity of polyethylene glycol modified enzymes, 98 -99 Aromatic monomers, limited biocompatibility, 155 Asparaginase, activity of polyethylene glycol modified enzymes, 98-99 Autacoids, inactivation during systemic delivery, 266-267... 

Argininosuccinate lyase (AL) (Fig. 40-5 reaction 4) cleaves argininosuccinate to form fumarate, which is oxidized in the tricarboxylic acid cycle, and arginine, which is hydrolyzed to urea and ornithine via hepatic arginase. Both AL and arginase are induced by starvation, dibutyryl cyclic-AMP and corticosteroids. 

The importance of manganese for bacteria, such as that of Ni and to a lesser extent Co, as we saw in the last chapter, is considerable. Of course, as we will see shortly, it is also important in the tetranuclear Mn cluster that is involved in oxygen production in photosynthetic plants, algae and cyanobacteria, as well as in a number of mammalian enzymes such as arginase and mitochondrial superoxide dismutase. Most of manganese biochemistry can be explained on the one hand by its redox activity, and on the other by its analogy to Mg2+ (reviewed in Yocum and Pecoraro, 1999). 

We begin this overview of manganese biochemistry with a brief account of its role in the detoxification of free radicals, before considering the function of a dinuclear Mn(II) active site in the important eukaryotic urea cycle enzyme arginase. We then pass in review a few microbial Mn-containing enzymes involved in intermediary metabolism, and conclude with the very exciting recent results on the structure and function of the catalytic manganese cluster involved in the photosynthetic oxidation of water. 

Figure 16.4 Dinuclear Mn centre of rat liver arginase. (From Ash, 2004. Copyright 2004, the American Society for Nutritional Science.)...

Nau WM, Ghale G, Hennig A et al (2009) Substrate-selective supramolecular tandem assays monitoring enzyme inhibition of arginase and diamine oxidase by fluorescent dye displacement from calixarene and cucurbituril macrocycles. J Am Chem Soc 131 11558-11570... 

Arginase 3.5.3.1 L-Arginine L-Ornithine/urea Urea-selective electrode... 

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