9419489 Randall A major point of interaction between photosynthesis, photorespiration and mitochondrial respiration is at the pyruvate dehydrogenase complex (PDC). This multi-enzyme complex is the primary entry point for carbon into the Krebs cycle for energy production and the generation of biosynthetic intermediates. PDC also provides the precursor for fatty acid biosynthesis, branch chain amino acids, isoprenoid compounds and some growth regulators. Objectives of this research are: to characterize the expression of PDC component enzymes, their mitochondrial import, processing and assembly in the complex; to characterize events, mechanisms and modulators of PDC activity during development and photosynthesis in C3, C4, and CAM plants; to extend biochemical characterization of PDC and establish in vitro and in organello regulatory mechanisms; and, to examine the long-term regulation/expression of PDC. Pea and Arabidopsis are the primary experimental systems used. This project will facilitate evaluation of the following concepts: that import and assembly of the mitochondrial matrix multi-enzyme cmplex, PDC, requires chaperones; that reversible phosphorylation of PDC is a primary control mechanism for carbon entry into the Krebs cycle; that PDC regulatory mechanisms differ during development and between C3, C4 and CAM plants.
