Профессионально-ориентированное чтение для магистров и аспирантов пищевых специальностей университета (сборник текстов). Михедова Л.Г. - 12 стр.

physicochemical character of soyabean protein, and cause the            Production of glutamate from glucose is not a simple
release of aglycones from isoflavone glucosides by B-               reaction. The major route shown with the heavy arrows in Fig. 1
glucosidase.                                                        involves at least 46 enzymatic steps. This major pathway
Terpstra et al. (1991) showed that the hamster is a useful animal   involves conversion of'glucose to phosphoenolpyruvate and
model for studying the effects of dietary proteins on lipid         pyruvate (C3) via the EMP pathway. These three-carbon
metabolism in the presence and absence of dietary cholesterol.      compounds are then converted to         ketoglutarate by reactions
Hamsters are known to have similar responses to human               involved in the early part of the TCA cycle. Since these
subjects with respect to dietary influences on blood lipids. An     organisms lack α-ketoglutarate dehydrogenase, which ordinarily
ethanol extract of isolated soyabean protein, which contains        would catalyze the next step in the TCA -cycle (the conversion
isoflavones, caused a more sensitive response to blood              of α -ketoglutarate to succinate), the α-ketoglutarate is instead
lipids in hamsters than in rats. (1600).                            converted to glutamate by reductive amination. The enzyme
                                                                    catalyzing this conversion is the NADP-specific glutamic acid
                                                                    dehydrogenase. The presence of this enzyme is essential to
                     Section IV                                     glutamate formation. If resting cells are incubated with glucose
                                                                    in the absence of ammonia, α.-ketoglutarate accumulates rather
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                                                                    than glutamate. It has been claimed that the content of glutamic
                                                                    acid dehydrogenase is much higher in glutamate excreters than
18. Biochemistry of the Glutamic Acid Fermentation                  in organisms which do not have this property; however, SHIIO et
                                                                    al. found Brevibacterium flavum and Escherichia coli to have,
    The production of glutamic acid from glucose by                 similar levels. The NADPH2 required for the action of glutamic
microorganisms in high yields is carried out byspecies of           acid dehydrogenase is supplied by the preceding isocitrate
Micrococcus,          Corynebacterium,           Brevibacterium,    dehydrogenase reaction. Glutamic acid dehydrogenase, in turn;
Microbacterium, Bacillus, and Arthrobacter. All of the species      provides the NADP required for the isocitrate dehydrogenase
of the above       genera which excrete glutamic acid are           step.
taxonomically similar and probably should be placed in a single         As mentioned above, the low content of α-ketoglutarate
genus. .Since practically all .forms of life produce this amino     dehydrogenase favors glutamate production. The enzyme has
acid, the glutamate excreters obviously possess special             been reported to be missing in Brev. Flavum to be low in
characteristics which allow them to excrete large quantities of     Brevibacterium divaricatum, and to be low. during the phase of
glutamate. These properties are a nutritional requirement for       glutamate excretion but to rise later in Bacillus megaterium. The
biotin and the lack, or very low content of, α-ketoglutarate        importance of the lack of this enzyme has been demonstrated
dehydrogenase. The biotin requirement is the major controlling      with E. coliwhich does not require biotin and is not a glutamate
factor involved in the fermentation. If enough biotin is supplied   excreter. Even without the biotin requirement a mutant which
for optimal growth, the organism produces lactate. Under            lacks α-ketoglutarate dehydrogenase was found to excrete 2.3
conditions of suboptimal growth, glutamate is excreted.             g/1 of glutamate while, its parent excreted nothing.