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Water Relations of Glucose‐catabolizing Enzymes in Pseudomonas fluorescens
Author(s) -
PRIOR B. A.,
KENYON C. P.
Publication year - 1980
Publication title -
journal of applied bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 0021-8847
DOI - 10.1111/j.1365-2672.1980.tb01220.x
Subject(s) - glucokinase , biochemistry , dehydrogenase , enzyme , chemistry , sucrose , glucose 6 phosphate dehydrogenase , glycerol , pseudomonas fluorescens , fructose , hexokinase , biology , glycolysis , bacteria , genetics
Examination of the catabolism of glucose via the Entner‐Doudoroff pathway by standard enzyme assays showed that the activity of glucose‐6‐phosphate dehydrogenase, glucokinase and 2‐ketoglu‐conokinase plus phosphoketogluconate reductase was completely inhibited at a w values less than 0.965, 0.98 and 0.96 respectively when NaCl was used to adjust the a w . The other glucose‐catabolizing enzymes were inhibited to a lesser degree. When sucrose was used to control a w , glucokinase and glucose‐6‐phosphate dehydrogenase were inhibited at 0.92 a w but the other enzymes remained active below 0.86 a w . Enzymes were relatively active at reduced a w when adjusted with glycerol and most remained active even at 0.80 a w . When a w was controlled by potassium glutamate, the activity of glucokinase and glucose‐6‐phosphate dehydrogenase was markedly less inhibited than by NaCl at similar a w . Possible reasons for the variation in activity by glucose‐catabolizing enzymes in response to a w controlled by various solutes could be location of the enzyme in the cell, ability of the solute to penetrate the cell and ability to withstand high salt and sucrose concentrations. When the a w of the growth medium was reduced to 0.98 by glycerol, NaCl and polyethylene glycol 400, levels of glucokinase were significantly reduced while higher levels of glucose dehydrogenase and gluconate dehydrogenase were induced. This suggests that reduction in a w could regulate the routes of catabolism in the Entner‐Doudoroff pathway. When sucrose was used to control a w of the growth medium high levels of most enzymes were induced, suggesting catabolism of the sucrose by the organism.