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Titolo:
Tricarboxylic acid cycle enzymes of the ectomycorrhizal basidiomycete, Suillus bovinus
Autore:
Grotjohann, N; Huang, Y; Kowallik, W;
Indirizzi:
Univ Bielefeld, Fak Biol, Lehrstuhl Stoffwechselphysiol, D-33501 Bielefeld, Germany Univ Bielefeld Bielefeld Germany D-33501 iol, D-33501 Bielefeld, Germany Peking Univ, Dept Urban & Environm Sci, Beijing 100871, Peoples R China Peking Univ Beijing Peoples R China 100871 ijing 100871, Peoples R China
Titolo Testata:
ZEITSCHRIFT FUR NATURFORSCHUNG C-A JOURNAL OF BIOSCIENCES
fascicolo: 5-6, volume: 56, anno: 2001,
pagine: 334 - 342
SICI:
0939-5075(200105/06)56:5-6<334:TACEOT>2.0.ZU;2-B
Fonte:
ISI
Lingua:
ENG
Soggetto:
NITROGEN-METABOLISM; GLUCOSE-UTILIZATION; GLYCOLYTIC-ENZYMES; CARBON; PHYSIOLOGY; MYCORRHIZA;
Keywords:
Suillus bovinus; carbohydrate metabolism; tricarboxylic acid cycle enzymes;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
31
Recensione:
Indirizzi per estratti:
Indirizzo: Grotjohann, N Univ Bielefeld, Fak Biol, Lehrstuhl Stoffwechselphysiol, Postfach 100131, D-33501 Bielefeld, Germany Univ Bielefeld Postfach 100131 Bielefeld Germany D-33501 ny
Citazione:
N. Grotjohann et al., "Tricarboxylic acid cycle enzymes of the ectomycorrhizal basidiomycete, Suillus bovinus", Z NATURFO C, 56(5-6), 2001, pp. 334-342

Abstract

In crude cell extracts of the ectomycorrhizal fungus, Suillus bovinus, activities of citrate synthase. aconitase, isocitrate dehydrogenase. succinatedehydrogenase. fumarase, and malate dehydrogenase have been proved and analyzed. Citrate synthase exhibited high affinities for both its substrates: oxaloacetate: (K-m = 0.018 mM) and acetyl-CoA (K-m = 0.014 mM). Aconitase showed better affinity for isocitrate (K-m = 0.62 mM) than for citrate (K-m = 3.20 mM). Analysis of isocitrate dehydrogenase revealed only small maximum activity (60 nmol x mg protein(-1) x min(-1)), the enzyme being exclusively NADP(+)-dependent. Using the artificial electron acceptor dichlorophenolindophenol, activity and substrate affinity of succinate dehydrogenase were rather poor. Fumarase proved Fe2+-independent. Its affinity for malate was found higher (K-m = 1.19 mM) than that for fumarate (K-m = 2.09 mM). Hightotal activity of malate dehydrogenase could be separated by native PAGE into a slowly running species of (mainly) cytosolic (about 80%) and a fasterrunning species of (mainly) mitochondrial origin. Affinities for oxaloacetate of the two enzyme species were found identical within limits of significance (K-m = 0.24 mM and 0.22 mM). The assumed cytosolic enzyme exhibited affinity for malate (K-m = 5.77 mM) more than one order of magnitude lower than that for oxaloacetate. FPLC on superose 12 revealed only one activity band at a molecular mass of 100 +/- 15 kDa. Activities of 2-oxoglutarate dehydrogenase and of succinyl-CoA synthetase could not be found. Technical problems in their detection, but also existence of an incomplete tricarboxylicacid cycle are considered. Metabolite affinities, maximum activities and pH-dependences of fumarase and of malate dehydrogenase allow the assumption of a reductive instead of oxidative function of these enzymes in vivo.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 06/04/20 alle ore 02:00:19