Ehrlich ascites tumor cells metabolized glutamine at a considerably higher rate under aerobic than under anaerobic conditions. Under both conditions ammonia was formed in amounts equivalent to the glutamine which disappeared. Under aerobic conditions the glutamine which disappeared could be largely accounted for as glutamate, aspartate, and alanine, whereas under anaerobic conditions only as glutamate.

Cells preincubated in air without glutamine showed higher aerobic glutamine utilization than did cells preincubated in nitrogen. Cells preincubated in nitrogen increased their aerobic glutamine utilization after a lag phase.

The increased aerobic glutamine utilization was shown not to be caused by increased cellular permeability for glutamine leading to a higher level of intracellular glutamine, and could not be linked to any of the enzymes known to utilize glutamine (glutaminase I, transaminases, glutamine synthetase, or l-amino acid oxidase).

Glutamine disappearance was little or not affected by 2,4-dinitrophenol or by inhibitors of the tricarboxylic acid cycle (malonate, trans-aconitate or As2O3), which increased glutamate formation from glutamine, mostly at the expense of aspartate. As2O3 also markedly reduced or abolished any stimulatory effect of glutamine on oxygen uptake. The results indicate that there exists a hitherto unknown glutamine deamidase reaction operating under aerobic conditions and with pH optimum around 7.5.

Bromthymol blue (10-3m) was found to exert a pronounced stimulatory effect on glutamine deamidation in whole cells and cell homogenates with formation of glutamate and ammonia. The effect occurred under both aerobic and anaerobic conditions.

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This investigation was supported by grants from Landsforeningen mot Kreft and from Grosserer N.A. Stangs Legat til kreftsykdommers bekjempelse.

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