Glutamine decomposition

Effects of ammonium on mammalian cell cultures. (A) Effects of ammonium generated by glutamine metabolism. (B) Effects of ammonium generated by glutamine decomposition or by ammonium addition in the culture medium. 

EXTRACELLULAR SPACE (glutamine decomposition) OR MITOCHONDRIA (glutamine metabolism)... 

The specific rate of glutamine consumption (which takes into account glutamine decomposition) ... 

Another toxic metabolite is ammonia. It is released by spontaneous decomposition of glutamine and to a far greater extend produced as a metabolite in... 

The mutation of ThrlSl, Glyl82, or Glul83 to alanine, or of Glul83 to glutamine also completely inhibited the ATP or acetylphosphate-dependent Ca transport, without effect on the phosphorylation of the enzyme by ATP in the presence of Ca or by Pi in the absence of Ca [127]. The phosphoenzyme formed from ATP retained its ADP-sensitivity at low concentration and alkaline pH, but its rate of decomposition was much slower than that of the wild-type enzyme in the presence of EGTA. These observations implicate the 181-183 region in the conformational changes related to Ca translocation. 

A second method of activating the acid for esterification (see Section 7.6) is as the mixed anhydride. The mixed-anhydride reaction had been employed decades ago for preparing activated esters. However, it was never adopted because of its unreliability and the modest yields obtained. The method was fine-tuned (Figure 7.12), after reliable information on the properties of mixed anhydrides was acquired (see Section 2.8). Tertiary amine is required for esterification of the mixed anhydride to occur. The method is generally applicable, except for derivatives of asparagine, glutamine, and serine with unprotected side chains. The base also prevents decomposition that occurs when the activated derivative is a Boc-amino acid (see... 

Tissue electrodes [2, 3, 4, 5, 45,57], In these biosensors, a thin layer of tissue is attached to the internal sensor. The enzymic reactions taking place in the tissue liberate products sensed by the internal sensor. In the glutamine electrode [5, 45], a thick layer (about 0.05 mm) of porcine liver is used and in the adenosine-5 -monophosphate electrode [4], a layer of rabbit muscle tissue. In both cases, the ammonia gas probe is the indicator electrode. Various types of enzyme, bacterial and tissue electrodes were compared [2]. In an adenosine electrode a mixture of cells obtained from the outer (mucosal) side of a mouse small intestine was used [3j. The stability of all these electrodes increases in the presence of sodium azide in the solution that prevents bacterial decomposition of the tissue. In an electrode specific for the antidiuretic hormone [57], toad bladder is placed over the membrane of a sodium-sensitive glass electrode. In the presence of the antidiuretic hormone, sodium ions are transported through the bladder and the sodium electrode response depends on the hormone concentration. 

Plasma that cannot be analyzed instantaneously should be kept frozen at -20°C. Glutamine is particularly liable to decomposition, thereby yielding glutamic acid, but also the ninhydrin-negative pyroglutamic acid. It has even been claimed that y-aminobutyric acid can be formed from glutamine. Even at -20°C the decomposition of glutamine cannot be stopped completely. 

As previously stated, ammonium in cell culture medium is the product of glutamine metabolism and its spontaneous decomposition at 37°C. Negrotti et al. (1989) showed that the half-life for glutamine at 37°C and pH 7.2 is only 7 days. The effects of ammonium on cell metabolism are observed from concentrations as low as 2 mM, which is easily reached in culture systems (Table 4.2). For example, the spontaneous decomposition of glutamine can result in 0.1 mM ammonia per day (Butler and Spier, 1984). Anchorage-dependent cells grown on microcarriers produce between 2 and 3 mM ammonia after growth in a batch culture (Butler et al.,... 

Ozturk, S. S., and Palsson, B. O. (1990). Chemical decomposition of glutamine in cell culture media Effect of media type, pH, and serum concentration. Biotechnol. Prog. 6, 121-128. 

L-Glutamine occurs as white crystals or a crystalline powder. It is soluble in water and practically insoluble in alcohol and in ether. Its solutions are acid to litmus. It melts with decomposition at about 185°. 

The spontaneous decomposition in the medium of glutamine into ammonia can be represented by a first-order rate process with respect to the glutamine concentration, as shown in Equation 4.3.8. 

Tritsch GL Moore GE (1962) Spontaneous decomposition of glutamine in cell culture media. Experimental Cell Research 3 73-78. 

Decomposition Products. — Among the products of decomposition are amino-acids, such as glycocoll, leucin, asparaginic and glutaminic acids, alanin, phenylalanin, a-prolin, etc. Tyrosin is not present. 

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