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2001 (1)
1998 (1)
1Author    N. Orbert, G. Rotjohann3, Yi Huangb, Wolfgang Kowallik3, W. Kowallik@, Biologie Uni-Bielefeld, Norbert De, U. Grotjohann@biologie, Ni-Bielefeld, DeRequires cookie*
 Title    Tricarboxylic Acid Cycle Enzymes of the Ectomycorrhizal Basidiomycete, S u ill us bovinus  
 Abstract    In crude cell extracts o f the ectomycorrhizal fungus, Suillus bovinus, activities o f citrate synthase, aconitase, isocitrate dehydrogenase, succinate dehydrogenase, fumarase, and malate dehydrogenase have been proved and analyzed. Citrate synthase exhibited high affinities for both its substrates: oxaloacetate (K m = 0.018 m M) and acetyl-CoA (K m = 0.014 m M) . A con i­ tase showed better affinity for isocitrate (K m = 0.62 m M) than for citrate (K m = 3.20 m M) . Analysis of isocitrate dehydrogenase revealed only small maximum activity (60 nmol x mg protein-1 x m in-1), the enzyme being exclusively N A D P +-dependent. Using the artificial electron acceptor dichlorophenol indophenol, activity and substrate affinity of succinate d e­ hydrogenase were rather poor. Fumarase proved Fe2+-independent. Its affinity for malate was found higher (K m = 1.19 m M) than that for fumarate (K m = 2.09 m M) . High total activity of malate dehydrogenase could be separated by native PAGE into a slowly running species of (mainly) cytosolic (about 80%) and a faster running species of (mainly) mitochondrial origin. A ffinities for oxaloacetate of the two enzyme species were found identical within limits of significance (K m = 0.24 m M and 0.22 m M) . 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 o f 2-oxoglutarate dehydrogenase and of succinyl-CoA synthetase could not be found. Technical problems in their detection, but also existence of an incom plete tricarboxylic acid 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 o f these enzymes in vivo. 
  Reference    Z. Naturforsch. 56c, 334 (2001); received December 13 2000/January 26 2001 
  Published    2001 
  Keywords    Suillus bovinus, Carbohydrate M etabolism, Tricarboxylic Acid Cycle Enzymes 
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 TEI-XML for    default:Reihe_C/56/ZNC-2001-56c-0334.pdf 
 Identifier    ZNC-2001-56c-0334 
 Volume    56 
2Author    Wolfgang Kowallik, M. Einolf Thiemann, Yi Huang, Gerard Mutumba, Lisa Beermann, Dagmar Broer, Norbert GrotjohannRequires cookie*
 Title    Complete Sequence of Glycolytic Enzymes in the Mycorrhizal Basidiomycete, Suillus bovinus  
 Abstract    Axenic cultures of Suillus bovinus were cultivated in inorganic liquid medium with glucose as a carbon source at 25 °C and continuous supply of oxygen by aeration with compressed air in the dark. Exogenous fructose as sole carbon source yielded about 50% less increase in dry weight than glucose. This resulted from different uptake velocities. Sucrose as sole exogenous carbon source yielded no measurable increase in dry weight. In glucose cultures, activities of all glycolytic enzymes were found. Maximum specific activ­ ities varied largely (from about 60 [fructose 6-phosphate kinase] to about 20 000 [triosephos-phate isomerase] nmoles • mg protein-1 • m in-1). A pparent K m-values also varied over more than two orders of magnitude (0.035 m M [pyruvate kinase] to 6.16 m M [triosephosphate iso­ merase]). Fructose 6-phosphate kinase proved to be the fructose 2,6-bisphosphate-regulated type, aldolase the divalent cation-dependent (class II) type and glyceratephosphate mutase the glycerate 2,3-phosphate-independent type of the respective enzymes. Eight of the 10 enzymes exhibited pH-optima' between 7.5-8.0. Triosephosphate isomerase and pyruvate ki­ nase showed highest activities at pH 6.5. Regulatory sites within the glycolytic pathway of Suillus bovinus are discussed; fructose 6-phosphate kinase appears to be its main bottle neck. 
  Reference    Z. Naturforsch. 53c, 818—827 (1998); received March 12/April 24 1998 
  Published    1998 
  Keywords    Suillus bovinus, Glycolytic Enzymes, Class II Aldolase, Fructose 2, 6-bisphosphate-Dependent Fructose 6-Phosphate Kinase, Mycorrhiza 
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 TEI-XML for    default:Reihe_C/53/ZNC-1998-53c-0818.pdf 
 Identifier    ZNC-1998-53c-0818 
 Volume    53