Biochemistry mitochondrial effect

H8. Hong, C. H., Effects of mitochondrial DNA depletion and 4977 bp deletion on the apop-totic behaviors of human cells. Master s thesis. Institute of Biochemistry, National Yang-Ming University, Taipei, Taiwan, 2001. 

Complete elucidation of the mechanisms by which ricin kills target cells remains an area of active study, but it is clear that the A -glycosidase activity of RTA is the essential triggering event. Inhibition of protein synthesis precedes other detectable alterations in target cell biochemistry. Ricin blocks amino acid incorporation in cmde microsome preparations before changes occur in energy metabohsm or oxidative phosphorylation the toxin has essentially no effect on mitochondrial respiration in isolated mitochondria or tumor cells (Waller et al., 1966 Dirheimer et al., 1968 Lin et al., 1971). Likewise, the first observable cytotoxic effect of ricin in cell culture is typically the inhibition of protein synthesis, followed by a reduction in DNA synthesis (Lin et al., 1970 Lin et al., 1971 Onozaki et al., 1972 Refsnes et al., 1974 Nicolson et al., 1975 Olsnes et al., 1976 Refsnes et al., 1977). 

Paraquat and diquat exert their toxic effects in plants mainly by interacting with photos mthesis, and in animals (and, but probably to a much lesser extent, also in plants) by interacting with mitochondrial respiration. A detailed description of the processes of photosynthesis and mitochondrial respiration would require many pages and is beyond the scope of this book. However, as they are key to the discussion, the following paragraphs have been included to provide a brief overview which is summarised in Figure 2. If the reader is interested in a more detailed account, this can be obtained from any standard biochemistry textbook. 

Ramirez, R., Sener, A., and Malaisse, W.J., 1995. Hexose metabolism in pancreatic islets effect of D-glucose on the mitochondrial redox state. Molecular and Cellular Biochemistry. 142 43-48. 

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