ZfN: Search Results

1	Author	BenjaminF. Matthews, JackM W Idholm	Requires cookie*
	Title	Expression of Aspartokinase, Dihydrodipicolinic Acid Synthase and Homoserine Dehydrogenase During Growth of Carrot Cell Suspension Cultures on Lysine-and Threonine-Supplemented Media
	Abstract	Reduction in the amounts o f activity o f the first enzyme, aspartokinase (EC 2.7.2.4) and two branch-point enzymes, dihydrodipicolinic acid synthase (EC 4.2.1.52) and homoserine dehydrogen ase (EC 1.1.1.3), located in the pathway for the synthesis o f aspartate-fam ily am ino acids, oc curred when cell suspension cultures of Daucus carota L. var. Danvers were grown in media contain ing 2 m M threonine or 2 m M lysine, endproducts of the pathway. Activity o f the lysine-sensitive form of aspartokinase was decreased when cells were grown in medium containing lysine and the ac tivity of the threonine-sensitive form was decreased when cells were grown in m edium containing threonine. Activity o f the branch-point enzyme leading to threonine synthesis, hom oserine dehy drogenase, was decreased up to 70% in specific activity (units/m g protein) and relative activity (units/g fresh weight) when cells were grown in m edia containing lysine or threonine. Threonine had no effect on the relative activity of dihydrodipicolinic acid synthase, but decreased its specific activity. Lysine decreased the relative activity of the synthase by up to 40%, but had little effect on its specific activity. The decreased activities o f the enzymes were apparently not due to binding of the inhibitory amino acids to the enzymes since homogenization of cells in buffer with 2 m M lysi ne and threonine did not decrease the m easurable enzyme activities. These and other results pres ented suggest that both forms of the aspartokinase activity and homoserine dehydrogenase activi ty can be altered by supplementing the growth medium with lysine or threonine.
	Reference	Z. Naturforsch. 34c, 1177—1185 (1979); received June 18 1979
	Published	1979
	Keywords	Daucus carota, Suspension Cultures, Amino Acids, Enzyme Regulation
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	TEI-XML for	default:Reihe_C/34/ZNC-1979-34c-1177.pdf
	Identifier	ZNC-1979-34c-1177
	Volume	34

2	Author	Wilhelm Simonis, Johanna Lee-Kaden	Requires cookie*
	Title	Selektive
	Abstract	Wirkungen von Lindan (y-l,2,3,4,5,6-Hexachlor-cyclohexan) auf Photosynthese, Aminosäure — Membrantransport und Proteinsynthese bei Anacystis nidulans Selective Effects of Lindane (7-1,2,3,4,5,6 Hexachlorocyclohexane) on Photosynthesis, M embrane Transport of Amino Acids and Protein Synthesis in Anacystis nidulans Effects of the chlorinated hydrocarbon insecticide Lindane on membrane transport of two neu trale amino acids in the Cyanobacterium Anacystis nidulans (Synechococcus AN) were measured. In white light the L-Leucine incorporation into the protein fraction was inhibited, increasing with time. After 30 minutes the degree of inhibition was the same as the effect of DCMU (5X 10-6 m) on L-Leucine incorporation. 14C 02-fixation was also reduced at this time. At 717 nm, which en ables PS I activity allone, no inhibition was observed. The light energy dependent membrane transport itself of L-leucine in presence of CAM and of the non-metabolisable a-AIB in white light and in monochromatic light of 630 nm and of 717 nm were not influenced by Lindane. The different sites of Lindane action are discussed. It is assumed that in 30 minutes chiefly photo synthesis (PS II and C 02-fixation) is affected by Lindane, resulting in a suppression of protein synthesis caused by a depletion of intermediates of C 02-fixation.
	Reference	Z. Naturforsch. 34c, 1062—1065 (1979); eingegangen am 12. Juni 1979
	Published	1979
	Keywords	Anacystis nidulans, Lindane Effects, Amino Acids, Membrane Transport, Photosynthesis
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	TEI-XML for	default:Reihe_C/34/ZNC-1979-34c-1062.pdf
	Identifier	ZNC-1979-34c-1062
	Volume	34