Succinic oxidase

Cytochrome c oxidase activity in lung mitochondria of Fisher-344 rats was significantly decreased at 50 ppm (15%), 200 ppm (43%), and 400 ppm (68%) hydrogen sulfide compared to controls after a 4-hour exposure (Khan et al. 1990). Cytochrome c oxidase activity had returned to normal for animals exposed to 200 ppm, but not for those exposed to 400 ppm, by 24 hours postexposure. Succinate oxidase activity was reduced at 200 ppm (40%) and 400 ppm (63%) but was not affected at 50 ppm (Khan et al. 1990). 

Spectrophotometric studies on the succinate oxidase system of Taenia hydatigena. Comparative Biochemistry and Physiology, 20 867-75. 

Figure 3-11. Arrhenius plots of mitochondrial succinate oxidase activity ( ) and growth rate (O) of the hypocotyl plus radicle of Vigna radiata. [Data are from Raison and Chapman (1976) used by permission.].

Examples showing the relationship between the value of the intercept and the degree of response can be seen by comparing Equations 24 and 25 with 28 and 30. The differences in the two sets of intercepts are 0.27 and 0.29, indicating that a twofold increase in concentration is required to cause 100% inhibition of succinate oxidase over 15-20% inhibition. 

Membranes from S. acidocaldarius (DSM 639) contain a malonate-sensitive succinate oxidase that is inhibited by cyanide [30]. The difference spectrum of membranes is indicative of a b-type cytochrome and o- and a-type cytochrome oxidases but provides no indication of a c-type cytochrome. NADH partially reduces the cytochromes when cyanide is present, indicating the presence of a cyanide-resistant pathway [65]. 

Lewisite shares many biochemical mechanisms of injury with the other arsenical compounds. It inhibits many enzymes in particular, those with thiol groups, such as pyruvic oxidase, alcohol dehydrogenase, succinic oxidase, hexokinase, and succinic dehydrogenase. As is tme with mustard, the exact mechanism by which Lewisite damages cells has not been completely defined. Inactivation of carbohydrate metabolism, primarily because of inhibition of the pymvate dehydrogenase complex, is thought to be a key factor (Trammel, 1992). 

Higher cholesterol levels (correlated with exposure levels), higher blood creatinine levels, marked disturbances of the hepatic cytochrome P-450 content and of the associated microsomal monooxygenase system, as well as the inhibition of succinic-oxidase enzyme activity, may also be considered as nonspecific biomarkers of carbon disulfide exposure. More research, however, needs to be done in order to determine whether a direct correlation exists between these parameters and carbon disulfide exposure. 

In studying the effects of carbon disulfide exposure on enzyme systems of carbohydrate metabolism, McKee et al. (1943) observed that the succinic-oxidase system was inhibited. They noted a 10% decrease in the activity of this system. Carbohydrate metabolism is crucial in proper neural function thus, succinic-oxidase activity may serve as an appropriate biomarker of nervous system effects (McKee et al. 1943). 

Trifiuoroacetylating all of the lysine residues of cytochrome c leaves the Soret and visible spectrum of the molecule intact but destroys all activity with the succinate oxidase preparation (147). The blocking groups can be gently hydrolyzed away again to recover the intact protein with all lysines free and with 100% activity. 

In contrast to the mammalian succinate oxidase, this mitochondrial complex in large helminths such as F. hepatica, Ascaris lumbricoides and Monieza expansa, forms H2O2 from oxygen instead of water and is insensitive to cyanide, azide and antimyein. In addition, there is evidence that the mitochondria of these large helminths contain a functional branched respiratory chain system with two terminal oxidases cytochrome 0 and Ug. The major pathway with cytochrome o as its terminal oxidase is apparently linked with H2O2 formation (23). 

Fatty acid auxotrophs of cerevlslae have been extensively utilized to probe relationships between fatty acid unsaturation and enzymic activity. A major area of Investigation has been elucidation of the bases for loss of oxidative phosphorylation by yeast cultures characterized by less than ca. 20-30% unsaturated fatty acid (42-44). Much reduced or no activity In mitochondrial membranes with highly saturated fatty acyl compositions has been documented for cytochromes a, a3, b and c, mitochondrial ATPase, succinate oxidase and NADH oxidase (45-47). Fatty acids apparently mediate many mitochondrial functions... 

Succinate oxidase and cytochrome-c oxidase (inner membrane),... 

Studies on the changes in the E and activity of succinate oxidase of plant mitochondria (Raison and Chapman, 1976 Chapman et al., 1979) and in the photoreduction of NADP by chloroplasts (Shneyour et al., 1973) are discussed in detail in the sections that follow and provide good evidence that the function of some membrane-associated enzymes from plants is modulated by membrane lipid structure. 

Fig. 5. Changes in the of succinate oxidase activity and the temperature coefficient of spin label motion for mitochondria from mature tubers of Jerusalem artichoke (Jf. tuberosus L.) as a function of temperature. The membranes were labeled with 12NS for the temperature range 8°-37°C and with 16NS for the range — 8°-28°C. Tt and T, were determined as the temperatures at which the coefficient of motion changes. Succinate oxidase activity was determined in the presence of ADP at the temperatures indicated. (From data of Chapman et al., 1979.)...

Fig. 6. Changes in the Jf and 7, of mitochondrial membranes from artichoke tubers as a function of storage time. Artichokes were harvested at time 0 and stored at 4°C in wet vermicu-lite. 7, and 7, were determined by spin labeling as shown in Fig. 5. The upper part of the figure shows the , for succinate oxidase determined in the temperature range above 7, as shown in Fig. 5. (From L. Wright and J. Raison, unpublished data.)...

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