Glutamate oxidation

Fukami et al. (1959) found a close relatio iship between the insecticidal efficiency of rotenoids and the degree of glutamate oxidation inhibition. The effect is accompanied by a substantial decrease in oxygen uptake. Lindahl and Oberg (1961) found that rotenone inhibits the aerobic oxidation of pyruvate. This effect can be counteracted with methylene blue, which permits the conclusion that rotenone inhibits mitochondrial respiration by reducing the activity of NADH -dehydro-genase. Hull and Whereat (1967) came to similar conclusions from their experimental results. 

NADPH-GltS and Fd-GltS also catalyze the reverse reaction - glutamate oxidation forming ammonia and... 

Neubauer B) and Knoop (Ba) demonstrated in the early part of this century the metabolic interconversion of a-amino and a-keto acids. In 1920, Thunberg (S) observed that glutamate was oxidized in the presence of frog muscle, and, in 1936, Weil-Malherbe (4) prepared an extract from brain tissue which catalyzed glutamate oxidation and identified the product, a-ketoglutarate, as its 2,4-dinitrophenylhydrazone. 

Kaplan et al. (310) demonstrated that the 3-acetylpyridine and pyri-dine-3-aldehyde analogs of NAD are utilized by bovine GDH with a greater efficiency than NAD itself. This has been attributed (309) to the fact that the 3-acetylpyridine analog is incapable of binding at the amide subsite thus, since dissociation of reduced coenzyme may be the rate-limiting step in glutamate oxidation, the velocity with the modified coenzyme is enhanced. Replacement of the 5 -AMP moiety of the coenzyme by formycin, 2-aminopurine ribonucleoside, or 7-deazapurine ribonucleo-side diminishes, but does not abolish, catalytic activity (311) thus, the... 

This is the only reported instance of a pH optimum higher for reductive amination than for glutamate oxidation however, the concentration of glutamate that was used was equivalent to the K for glutamate at pH 7.6 and may well have been too low to saturate the enzyme over the pH range tested. 

Fig. 9 Signals recorded in vivo with glutamate microsensor and glutamate oxide-free background microsensor during the local injection of 200 nL of 100-tiM TTX via a micropipet The horizontal bar indicates the duration of the injection. The scale bar was calculated based on postcalibration results.

The oxidation of n-glutamate by the cyclophorase system requires the presence of AMP, Mg++, and Pi. Only with a well-aged cyclophorase preparation is there a stimulation of glutamate oxidation by added DPN. The authors state that the n- lutamic acid oxidase of Euler et al. and Dewan is involved, but that there is a difference in the state of the oxidase in the two systems. In the cyclophorase preparation the enzyme is fully conjugated, whereas in the isolated enzyme the protein is dissociated from the pyridine nucleotide. 

With crystalline beef liver glutamic dehydrogenase the specific activity was 90 for glutamate oxidation and 950 for utamate formation 89). The reported specific activities of the chicken liver enzyme were 183 and 1350, respectively 91). 

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