Ammonia AMP

Various amines find application for pH control. The most commonly used are ammonia, morpholine, cyclohexylamine, and, more recently AMP (2-amino-2-methyl-l-propanol). The amount of each needed to produce a given pH depends upon the basicity constant, and values of this are given in Table 17.4. The volatility also influences their utility and their selection for any particular application. Like other substances, amines tend towards equilibrium concentrations in each phase of the steam/water mixture, the equilibrium being temperature dependent. Values of the distribution coefficient, Kp, are also given in Table 17.4. These factors need to be taken into account when estimating the pH attainable at any given point in a circuit so as to provide appropriate protection for each location. 

Condensation of CO2, ammonia, and ATP to form carbamoyl phosphate is catalyzed by mitochondrial carbamoyl phosphate synthase I (reaction 1, Figure 29-9). A cytosolic form of this enzyme, carbamoyl phosphate synthase II, uses glutamine rather than ammonia as the nitrogen donor and functions in pyrimidine biosynthesis (see Chapter 34). Carbamoyl phosphate synthase I, the rate-hmiting enzyme of the urea cycle, is active only in the presence of its allosteric activator JV-acetylglutamate, which enhances the affinity of the synthase for ATP. Formation of carbamoyl phosphate requires 2 mol of ATP, one of which serves as a phosphate donor. Conversion of the second ATP to AMP and pyrophosphate, coupled to the hydrolysis of pyrophosphate to orthophosphate, provides the driving... 

The concept of a biocatalytic membrane electrode has been extended to the use of a tissue slice as the catalytic layer. An example of this approach is an electrode for AMP which consists of a slice of rabbit muscle adjacent to an ammonia gas electrode. NHj is produced by enzymatic action of rabbit muscle constituents on AMP The electrode exhibits a linear range of 1.4 x 10 to 1.0 x 10 M with a response time varying from 2.5 to 8.5 min, depending on the concentration. Electrode lifetime is about 28 days when stored between use in buffer with sodium azide to prevent bacterial growth. Excellent selectivity enables AMP to be determined in serum. 

MePO2- or PME2- (Table XIX), but the open closed equilibrium lies very much on the side of the chelated form of the complex (87% for the Ca2+ complex - compare 15% for [Ca(atp)]2 and just 7% for [Ca(amp)] (695)). The availability of stability constants both for methylphosphonate and for benzimidazole (a purine model) complexes means that the chelate effect for complexes of (1H-benzimidazol-2-yl-methyl)phosphonate can be discussed without the usual complications, such as the differences between ethane-1,2-diamine and two ammonia or two methylamine ligands and disparities between units (704). 

Deficiency of the muscle-specific myoadenylate deaminase (MADA) is a frequent cause of exercise-related myopathy and is thought to be the most common cause of metabolic myopathy. MADA catalyzes the deamination of AMP to IMP in skeletal muscle and is critical in the purine nucleotide cycle. It is estimated that about 1-2% of all muscle biopsies submitted to medical centers for pathologic examination are deficient in AMP deaminase enzyme activity. MADA is 10 times higher in skeletal muscle than in any other tissue. Increase in plasma ammonia (relative to lactate) after ischemic exercise of the forearm may be low in this disorder, which is a useful clinical diagnostic test in patients with exercise-induced myalgia... 

Nucleotidase 3.1.3.5 C 5 -AMP NADH Adenosine Ammonia Adenosine deaminase Glutamate dehydrogenase... 

Within a cell, a nncleotidase catalyses the hydrolysis of either a ribonncleotide or deoxyribonucleotide (Fignre 10.8). The qnantitatively important pathway for degradation of AMP in liver and mnscle involves deamination to IMP, catalysed by AMP deaminase, producing ammonia, and snbseqnent hydrolysis of IMP to inosine. This may be an important sonrce of inosine for synthesis of phosphati-dylinositol, a key phospholipid in membranes. 

This enzyme [EC 3.S.4.6], also known as AMP amino-hydrolase and adenylic acid deaminase, catalyzes the hydrolysis of AMP to yield IMP and ammonia. 

GMP synthetase [EC 6.3.4.1], also known as xanthosine-5 -phosphate ammonia ligase, catalyzes the reaction of ATP with xanthosine 5 -phosphate and ammonia to produce GMP, AMP, and pyrophosphate (or, diphosphate). GMP synthetase (glutamine-utilizing) [EC 6.3.5.2] catalyzes the reaction of ATP with xanthosine 5 -phosphate, L-glutamine, and water to produce GMP, AMP, L-glutamate, and pyrophosphate. 

See Ammonia as a substrate or product AMOUNT-OE-SUBSTANCE CONCENTRATION AMP... 

Figure 6. Instrumental schematic for vacuum UV photofragmentation-laser induced fluorescence measurement of ammonia SHGC, second harmonic generation crystal SFMC, sum frequency mixing crystal BS, beam splitter BD, beam dump TP, turning prism CL, cylindrical lens R, reflector TD, trigger diode OSC, oscillator cell AMP, amplifier cell BE, beam expander G, grating OC, output coupler M, mirror BC, beam combiner L, lens A, aperture PD, photodiode SC, sample cell RC, reference cell FP, filter pack SAM.PMT, sample cell photomultiplier REF.PMT, reference cell photomultiplier PP, additional photomultiplier port EX, exhaust and CGI, calibration gas inlet to flow line. (Reproduced with permission from reference 15. Copyright 1990 Optical Society of America.)...

Thiocysteine can also arise in a similar manner through action of cystathionine (3 lyase on cystine. Thiocysteine is eliminated with production of pyruvate and ammonia from the rest of the cystine molecule 467 One of the nifS-like proteins of E. coli is thought to transfer a selenium atom from selenocysteine (pp. 823-827) into selenophosphate 466a f The latter can be formed by transfer of a phospho group from ATP to selenide HSe-. The other products of ATP cleavage are AMP and P . Reduction of Se° to HSe- is presumably necessary. 

Muscular work is accompanied by the production of ammonia, the immediate source of which is adenosine 5 -phosphate (AMP).301 302 This fact led to the recognition of another substrate cycle (Chapter 11) that functions by virtue of the presence of a biosynthetic pathway and of a degradative enzyme in the same cells (cycle A, Fig. 25-17). This purine nucleotide cycle operates in the brain303 304 as well as in muscle. The key enzyme 5-AMP aminohydrolase (AMP deaminase step a, Fig. 25-17) also occurs in erythrocytes and many other tissues.304 305 Persons having normal erythrocyte levels but an absence of this enzyme in muscles suffer from muscular weakness and cramping after exercise.306... 

Our studies of the substrates [glutamate (I) and ATP] and of substrate analogs [AMP-P-(CH2)-P and methionine sulfoximine] reveal interactions between both substrate sites and both metal ion sites. Previously mentioned studies by Meister s group showed that the irreversible inhibition of glutamine synthetase in the presence of L-methionine (S)-sulfoximine and ATP was due to formation of the sulfoximine phosphate (IV). The tetrahedral geometry at the sulfur atom of the sulfoximine was suggested to be a mimic of the active structure of the adduct of y-glutamyl phosphate and ammonia (III). Data in our laboratory provide spectroscopic evidence that methionine... 

The existence of two separate enzymes in animal tissues responsible for the liberation of ammonia from each of the two aminopurines, adenine and guanine, the latter specific for the free purine and the former for the nucleosides, was initially presented by Jones and his colleagues 11, 12). In 1928, Schmidt 13-15) demonstrated that AMP aminohy-drolase was responsible for the appearance of inosinic acid in muscle and for at least a portion of ammonia liberated during contraction. He showed not only a marked specificity for deamination of 5 -AMP but also provided the first clue that muscle adenylic acid (5 -AMP) and yeast adenylic acid (3 -AMP) were different compounds. Initial evidence for guanine and adenosine aminohydrolase including aspects of the specificity were also described by Schmidt 16). Additional details regarding development of interest in purine aminohydrolases are available in several excellent reviews 17-20). 

According to R. Ihle, the formation of ammonia at the cathode in the electrolysis of nitric acid depends on the current density and the cone, of the acid. Thus, for acids of 14-67, 28-73, 43-34, and 85-37 per cent. HN03, current densities of 0-00159, 0-01122, and 0-0564, and 8-6 amps, per sq. cm. were respectively required before any trace of ammonia was obtained. With increased current, the quantity of ammonia formed was also increased. J. F. Daniell noted the formation of ammonia at the cathode during the electrolysis of an aq. soln. of potassium nitrate. G. E. Cassel obtained ammonia by the electrolysis of soln. of nitrates. 

J. Tafel electrolyzed a soln. of 0-4 grm. of nitric acid and 20 c.c. of 50 per cent, sulphuric acid, using 10 sq. ems. of cathode surface and 2-4 amps, at 0°. The product of the reduction is largely dependent on the nature of the metal used as electrode. Some results are indicated in Table XXVII. With platinum, no ammonia or hydroxylamine was formed, and with palladium the reduction is extremely slow. Hie chief products of the reduction are hydroxylamine and ammonia. The largest proportion of the hydroxylamine is formed when mercury is used as cathode, and the conversion of the nitric acid into this can be carried out almost quantitatively. With lead electrodes, about 40 per cent, of the nitric acid is converted into hydroxylamine, and with copper electrodes only about 15 per cent. if the copper be in the form of a spongy mass, only about one per cent, of the acid is transformed into hydroxylamine, the remainder being reduced to ammonia. When... 

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