Release of amino-acids

Figure 4. Enzymatic hydrolysis of met-enkephalin (2.5 nmol) showing the sequential release of amino acids and the final mixture. The amino acids were identified from the retention times of the standard amino acid mixture 9, Gly 12, Tyr 14, Met 17, Phe. (Reprinted from reference 5. Copyright 1987 American Chemical Society.)...

The cortical cup has been used for many years to monitor changes in transmitter release induced by physiological and pharmacological stimuli (Fig. 4.5). In the past, it was used most commonly to study release of amino acids and acetylcholine. More recently, it has... 

Figure 4.4 Release of amino acids from cortical slices exposed to 50 mM K+. Measurements by HPEC and fluorescence detection after reaction of amino acids with o-phthalaldehyde 1, aspartate 2, glutamate 3, asparagine 4, serine 5, glutamine 6, histidine 7, homoserine (internal standard) 8, glycine 9, threonine 10, arginine 11, taurine 12, alanine 13, GABA 14, tyrosine. Glutamate concentration is almost 1 pmol/gl which represents a release rate of 30 pmol/min/mg tissue...

Dodd, PR and Bradford, HF (1976) Release of amino acids from the mature cobalt induced epileptogenic focus. Brain Res. Ill 377-388. 

A new approach to study root exudation of distinct compounds in soil-grown plants uses inoculation of roots with genetically engineered reporter bacteria, which are able to indicate the presence of particular compounds by indicator reactions, such as production of ice-nucleation proteins. This technique has been employed to detect the release of amino acids from roots of soil-grown A vena harbata (56). 

Bianchi L, Colivicchi MA, Bolam JP, Della Corte L. 1998. The release of amino acids from rat neostriatum and substantia nigra in vivo a dual microdialysis probe analysis. Neuroscience 87(1) 171-180. 

The synthesis of active centers is not a small problem. The enzyme car-boxypeptidase A is a pancreatic exopeptidase that catalyzes the sequential release of amino acids from the C terminus of polypeptide chains as shown in reaction (1). Much work has been done on the structure 31). Although the... 

Hormones can modify the concentration of precursors, particularly the lipolytic hormones (growth hormone, glucagon, adrenaline) and cortisol. The lipolytic hormones stimulate lipolysis in adipose tissue so that they increase glycerol release and the glycerol is then available for gluconeogenesis. Cortisol increases protein degradation in muscle, which increases the release of amino acids (especially glutamine and alanine) from muscle (Chapter 18). 

Metabolism/Excretion - Lepirudin is thought to be metabolized by release of amino acids via catabolic hydrolysis of the parent drug however, conclusive data are not available. Approximately 48% of the administered dose is excreted in the urine, which consists of unchanged drug (35%) and other fragments of the parent drug. 

Dispostion Lepirudin is ehminated primarily by renal excretion. It may be metabolized by release of amino acids via catabohc hydrolysis of the parent drug. 

The glucocorticoids have important dose-related effects on carbohydrate, protein, and fat metabolism. The same effects are responsible for some of the serious adverse effects associated with their use in therapeutic doses. Glucocorticoids stimulate and are required for gluconeogenesis and glycogen synthesis in the fasting state. They stimulate phosphoenolpyruvate carboxykinase, glucose-6-phosphatase, and glycogen synthase and the release of amino acids in the course of muscle catabolism. 

The net results of these actions are most apparent in the fasting state, when the supply of glucose from gluconeogenesis, the release of amino acids from muscle catabolism, the inhibition of peripheral glucose uptake, and the stimulation of lipolysis all contribute to maintenance of an adequate glucose supply to the brain. 

Release of amino acid derivative by acid hydrolysis... 

Phillis J. W. and O Regan M. H. (1995). GM1 ganglioside inhibits ischemic release of amino acid neurotransmitters from rat cortex. NeuroReport 6 2010-2012. 

Other types of reactions which have been studied using FABMS include those catalyzed by enzymes. This application is particularly interesting because it represents for the first time a generally useful and molecularly specific probe with which to measure a wide variety of enzyme substrates and products. Two approaches have been successful, one in which the reaction is followed by the removal of aliquots of sample taken at timed intervals with subsequent analysis by FABMS and the other allowing the reaction to take place in a glycerol-water mixture on the probe directly inside the mass spectrometer. The choice of either method depends upon the application. If the prime interest is to analyze a substrate, for example, monitoring the release of amino acids from a polypeptide using an exopeptidase, then direct analysis inside the spectrometer may be preferred. If, on the other hand, the prime interest lies... 

Armstrong, S. M., and F. Barlocher. 1989. Adsorption and release of amino acids from epilithic biofilms in streams. Freshwater Biology 22 153—159. 

Schweitzer, B., I. Huber, R. Amann, W. Ludwig, and M. Simon. 2001. Alpha- and beta-Proteobacteria control the consumption and release of amino acids on lake snow aggregates. Applied and Environmental Microbiology 67 632-645. 

An important harmful effect of metals at the cellular level is the alteration of the plasma membrane permeability, leading to leakage of ions like potassium and other solutes (Passow and Rothstein, 1960 Wainwright and Woolhouse, 1978 De Filippis, 1979 De Vos et al., 1988, 1991). After supply of copper ions Ohsumi et al. (1988) demonstrated for yeast cells and De Vos et al. (1989) for root cells of Silene cucubalus that the permeability barrier (controlled by means of potassium leakage) of the plasma membrane was almost immediately lost. Oshumi et al. (1988) also reported a quick release of amino acids, especially glutamate and aspartate. After McBrien and Hassall (1965) and Overnell (1975), who studied potassium release from algal cells, the increased permeability of the plasma membrane may be considered to constitute the primary toxic effect of copper. 

The enzyme carboxypeptidase A hydrolyzes amino acids from the C-terminal end of peptides, provided that the C-terminal residue is not proline, lysine, or arginine. Fig. 4-13 shows the sequential release of amino acids from a protein by means of treatment with carboxypeptidase A. Deduce the sequence at the C terminus. 

Benjamin AM, Quastel JH (1972) Locations of amino acids in brain slices from the rat. Tetrodotoxin-sensitive release of amino acids. Biochem J 128 631-646... 

Estimates of N2 fixation rates in the global ocean continue to rise as results emerge from studies with the main N2 fixer in the ocean Trichodesmium, the heterocystous endosymbiont Richelia, as well as more recently discovered N2 fixers including unicellular diazotrophic cyanobacteria and bacterioplankton (Capone et al, 1997 HanseU and Feely 2000 Karl et al, 1997 Lipschultz and Owens, 1996 Montoya et al., 2004 Zehr et al, 1998 and 2001). Trichodesmium is involved in N release directly, through release of amino acids, DON, and NH4 (reviewed in Table 8.2). Trichodesmium is also a source of NH4+ and DON as a result of remineralization by associated bacteria, sloppy feeding and excretion by grazers (SeUner, 1992 Sheridan et al, 2002). 

Andersson, A., Lee, C., Azam, F., and Hagstrom, A. (1985). Release of amino acids and inorganic nutrients by heterotrophic marine microflageUates. Mar. Ecol. Prog. Ser. 23, 99—106. 

In order to test these hypotheses, we conducted a filtration study using a small pilot unit. This permitted us to better control back working parameters. To explore the possible release of amino acids, tbe study employed a filter partially colonized by bacteria. 

This pilot-scale has confirmed our earlier observations from full-scale drinking-water treatment plants. Such a detailed and systematic analysis of the amino acid concentrations allow one to monitor the degree of colonization of the filter media. Such colonization presents a problem when it is not wanted or improperly controlled. In these cases, it may be possible to disinfect and then wash the filtey media to decrease the release of amino acids. 

Carboxypeptidase is an exopeptidase that specifically hydrolyzes the C-terminal peptide bond and releases the C-terminal amino acid. Two problems are associated with its use the substrate specificity of the enzyme and the continuous action of the enzyme. The continuous action may yield the second, third, and additional residues from some chains even before the terminal residues on every chain are quantitatively released. Thus, it may be difficult to determine which residue is the C terminus. However, monitoring the sequential release of amino acids can often reveal the sequence of several residues at the C terminus. Concerning specificity, carboxypeptidase A releases all C-terminal residues except Lys, Arg, and Pro carboxypeptidase B cleaves C-terminal Arg and Lys residues and carboxypeptidase C hydrolyzes C-terminal Pro residues. Thus, more than one method may be needed to establish the C-terminal amino acid. 

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