[Seminars] PSB event reminder

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Calendar Name: seminars
Scheduled for: Tuesday, May 18 2010, 11:00 - 12:30
Event text:    Prof Richard C. Leegood
	       
	       Robert Hill Institute & Department of Animal and Plant
	       Sciences
	       University of Sheffield
	       UK
Details:       "PEP Carboxykinase in Plants: An Enzyme for all Seasons"
	       
	       ABSTRACT
	       
	       Phosphoenolpyruvate carboxykinase (PEPCK) catalyses the
	       reversible nucleotide triphosphate (GTP- or ATP-)
	       -dependent decarboxylation of oxaloacetate to PEP and
	       CO2. The ATP-dependent enzyme is present in flowering
	       plants, fungi, algae and many bacteria, the related
	       GTP-dependent enzyme in animal tissues. PEPCK is present
	       in many plant tissues and appears to be located
	       exclusively in the cytosol, although it may be plastidic
	       in diatoms. It is regulated in some, but not all, plant
	       tissues by reversible protein phosphorylation. Some of
	       its functions in plants are well understood, such as its
	       role in the photosynthetic CO2-concentrating mechanisms
	       of C4 photosynthesis (including diatoms) and in
	       Crassulacean Acid Metabolism. In these, PEPCK provides
	       CO2 for the Calvin cycle by decarboxylating OAA derived
	       from C4 acids. Its role in gluconeogenesis following
	       germination of fat-storing seeds is also well studied.
	       However, in recent years it has become clear that PEPCK
	       is present in only certain types of cells and that its
	       abundance is often dependent on developmental stage. It
	       thus functions in far more metabolic processes in plants
	       than was previously realised, but, as in many animal
	       tissues, its function has been less easy to discern.
	       Within leaves, although not abundant overall, it may be
	       present in phloem companion cells, hydathodes, trichomes
	       and stomata. In stomata, data from Arabidopsis
	       knock-outs suggest that it plays an important role in
	       stomatal closure. It has been identified in a range of
	       tissues, such as developing seeds, flowers, roots,
	       vascular tissue and fruit. In developing pea or grape
	       seeds laying down storage proteins it is implicated in
	       the metabolism of incoming nitrogenous compounds. This
	       seminar will outline the regulation of the activity of
	       PEPCK in plants and discuss some of its physiological
	       functions.

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