Showing papers by "Sharon A. Robinson published in 1992"
TL;DR: Findings strengthen the view that the function of GDH is the catabolism of glutamate, which under conditions of carbon stress provides carbon skeletons for tricarboxylic acid cycle activity.
Abstract: Glutamate dehydrogenase (GDH) specific activity and function have been studied in cell suspension cultures of carrot (Daucus carota L. cv Chantenay) in response to carbon and nitrogen supply in the culture medium. The specific activity of GDH was derepressed in sucrose-starved cells concomitant with protein catabolism, ammonium excretion, and the accumulation of metabolically active amino acids. The addition of sucrose led to a rapid decrease in GDH specific activity, an uptake of ammonium from the medium, and a decrease in amino acid levels. The extent of GDH derepression was correlated positively with cellular glutamate concentration. These findings strengthen the view that the function of GDH is the catabolism of glutamate, which under conditions of carbon stress provides carbon skeletons for tricarboxylic acid cycle activity.
117 citations
TL;DR: In this article, the authors measured the oxygen fractionation of samples in a gas-phase leaf disk electrode unit and calculated the partitioning of electron transport to these pathways from measurements of discrimination in the absence of inhibitors.
Abstract: Discrimination against 18O during dark respiration in tissues of Kalanchoe daigremontiana, Medicago sativa, and Glycine max was measured using an on-line system that enabled direct measurements of the oxygen fractionation of samples in a gas-phase leaf disk electrode unit. Discrimination factors for cytochrome pathway respiration were 18.6 to 19.8%o for all tissues. However, discrimination in cyanide-resistant respiration was significantly higher in green tissues (30.4-31.2%o) compared with nongreen tissues (25.3-25.9%o). Using these discrimination factors, the partitioning of electron transport to these pathways was calculated from measurements of discrimination in the absence of inhibitors. Changes in flux through the alternative pathway were measured during the light and dark phases of Crassulacean acid metabolism in leaf disks of K. daigremontiana. The flux of electrons through the alternative pathway was higher during deacidification than during the other phases of Crassulacean acid metabolism. The increase in alternative pathway electron flux accounted for all of the increased respiration in the light phase. Despite this increase, simultaneous measurements of malate concentration and respiratory flux confirm that only a small proportion of the total malate decarboxylation occurs in the mitochondria.
100 citations
18 citations