Glucose metabolism in Xanthomonas campestris and influence of methionine on the carbon flow.
The glucose flow in Xanthomonas campestris was investigated with radio-labelled glucose and by enzymological studies. Only 7% of the radioactivity was incorporated into the cell material, but 41% was oxidized to carbon dioxide and 28% transformed to xanthan. Up to 16% of cell dry weight consisted of the polysaccharide glycogen. In the presence of 2.7 mM methionine, which is an inhibitor of xanthan formation, increased carbon dioxide formation (51%) occurred. This increase was in accordance with a twofold increase in the NAD-dependent isocitrate dehydrogenase activity. The other carbon dioxide liberating enzyme, 6-P-gluconate dehydrogenase, was not influenced by methionine, but its occurrence indicates the presence of an active pentose phosphate pathway in X. campestris. Among the other enzymes detected in X. campestris was glucose dehydrogenase. The presence of this enzyme together with hexokinase indicates the operation of two different glucose metabolizing steps: one oxidative, the other phosphorylative. Only the latter directly provides phosphorylated glucose as a precursor for the activated sugars required for xanthan synthesis.
Pielken
P
P
Institute of Biotechnology 1, Nuclear Research Centre Jülich, Federal Republic of Germany.
Schimz
K L
KL
Eggeling
L
L
Sahm
H
H
D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D005948:Glucose Dehydrogenases / Q000032:analysis; D006003:Glycogen / Q000032:analysis; D006593:Hexokinase / Q000032:analysis; D007521:Isocitrate Dehydrogenase / Q000032:analysis; D008715:Methionine / Q000378:metabolism*; D010734:Phosphogluconate Dehydrogenase / Q000032:analysis; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis; D014974:Xanthomonas / Q000201:enzymology / Q000378:metabolism*
D011135:Polysaccharides, Bacterial; D002245:Carbon Dioxide; D002244:Carbon; D006003:Glycogen; D008715:Methionine; D005948:Glucose Dehydrogenases; D007521:Isocitrate Dehydrogenase; D010734:Phosphogluconate Dehydrogenase; C029757:phosphogluconate dehydrogenase (decarboxylating); D006593:Hexokinase; D005947:Glucose; C002563:xanthan gum