. Biological structure and function; proceedings. Biochemistry; Cytology. INTEGRATED OXIDATIONS IN ISOLATED MITOCHONDRIA 75 which in this case is directly oxidized by the cytochrome system, since, even in mitochondria depleted of their endogenous substrates, glutamate was oxidized immediately and rapidly. This was also the case when ^-hydroxybutyrate, proline and malate served as substrates. However, even when glutamate is oxidized by the dehydrogenase pathway, the rate of this reaction is intimately dependent upon the rate at which a-ketoglutarate is removed. This can be shown clearly by a st
. Biological structure and function; proceedings. Biochemistry; Cytology. INTEGRATED OXIDATIONS IN ISOLATED MITOCHONDRIA 75 which in this case is directly oxidized by the cytochrome system, since, even in mitochondria depleted of their endogenous substrates, glutamate was oxidized immediately and rapidly. This was also the case when ^-hydroxybutyrate, proline and malate served as substrates. However, even when glutamate is oxidized by the dehydrogenase pathway, the rate of this reaction is intimately dependent upon the rate at which a-ketoglutarate is removed. This can be shown clearly by a study of the effects of/S-chlorovinylarsenious oxide on glutamate oxidation (Fig. 5). 100 90 80 B 70 I 60 : 50 > ° 40 <v 30|- 20I-' 10. -»- 0 OS 1-0 1-5 20 25 ^/S-chlorovinylarsenious oxide (/^g/4ml,) Fig. 5. The eflFect of ^-chlorovinylarsenious oxide on ADP-stimulated oxida- tion of glutamate (x — x ), a-ketoglutarate (D—D), succinate (H h) and proline(c—c). This arsenical inhibited oxidation of glutamate and a-ketoglutarate to the same extent at the same concentrations. Under identical conditions j8-hydroxybutyrate, malate, proline, and succinate oxidation and the associated phosphorylation were unaffected. The inhibitory effect was readily reversed by 2 :3-dimercaptopropanol (Fig. 6). The arsenical, at these concentrations, does not inhibit the glutamate dehydrogenase itself, since in disrupted mitochondria, when DPN and cytochrome c were added, /S-chlorovinylarsenious oxide did not inhibit glutamate oxidation. In intact mitochondria it appears that glutamate oxidation cannot occur when a-ketoglutarate accumulates. Alternatively it may be concluded that the glutamate dehydrogenase is not functional in intact liver mitochondria and only serves to "spark" the oxidation of glutamate by the transaminase. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of
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