Submitted to: European Journal of Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/29/2002
Publication Date: 3/1/2003
Citation: TOVAR-MENDEZ, A., MIERNYK, J.A., RANDALL, D.D. REGULATION OF PYRUVATE DEHYDROGENASE COMPLEX ACTIVITY IN PLANT CELLS. EUROPEAN JOURNAL OF BIOCHEMISTRY. 2003. v. 270. p. 1043-1049. Interpretive Summary: Respiration is the use of energy by living cells to do work. Growth and reproduction are both directly coupled to the rates of respiration. It is essential that respiration be carefully controlled or wasted energy would decrease crop yields and reduce agricultural productivity. The control of respiration in plant cells is a subject of ongoing study. A complex of several proteins that is critical for the regulation of respiration was isolated and characterized. The two forms of the protein complex are located in different components of plant cells. One form is more similar to the corresponding complex from bacteria while the other is more similar to the complex from animal cells. The mechanisms of interaction between the two distinct, spatially separate forms of the complex are unique to plant cells. This information will be important to researchers in their attempts to increase agricultural productivity by improving the control of plant cell respiration, and to other plant scientists who will try to design more efficient crop plants through either classical breeding or biotechnology.
Technical Abstract: The pyruvate dehydrogenase complex (PDC) is subjected to multiple interacting levels of control in plant cells. The first level is subcellular compartmentation. Plant cells are unique in having two distinct, spatially separated forms of the PDC; mitochondrial (mtPDC) and plastidial (plPDC). The mtPDC is the site of carbon entry into the tricarboxylic acid cycle, while the plPDC provides acetyl-CoA and NADH for de novo fatty acid biosynthesis. The second level of regulation of PDC activity is the control of gene expression. The genes encoding the subunits of the mt- and plPDCs are expressed following developmental programs, and are additionally subject to physiological and environmental cues. Thirdly, both the mt- and plPDCs are sensitive to product inhibition, and, potentially, to metabolite effectors. Finally, the two different forms of the complex are regulated by distinct organelle-specific mechanisms. Activity of the mtPDC is regulated by reversible phosphorylation catalyzed by intrinsic kinase and phosphatase components. An additional level of sensitivity is provided by metabolite control of the kinase activity. The plPDC is not regulated by reversible phosphorylation. Instead, activity is controlled in large part by the physical environment that exists in the plastid stroma.