Glucose-fructose oxidoreductase, a new enzyme isolated from Zymomonas mobilis that is responsible for sorbitol production.

AUTOR(ES)

Zachariou, M

RESUMO

The enzymes responsible for sorbitol formation in Zymomonas mobilis were investigated. A previously undescribed enzyme catalyzes the intermolecular oxidation-reduction of glucose and fructose to form gluconolactone and sorbitol. This enzyme has been purified; it had a subunit size of 40,000 daltons and is probably tetrameric at low pH. It contained tightly bound NADP as the hydrogen carrier and did not require any added cofactor for activity. In addition, a gluconolactonase has been isolated, although not completely purified. Together these two enzymes were capable of completely converting a 54% (wt/vol) equimolar mixture of glucose and fructose to sorbitol and sodium gluconate at the optimum pH of close to 6.2. The oxidoreductase had low affinities for its substrates, but natural environmental conditions would expose it to high concentrations of sugars. The amount of the enzyme in Z. mobilis cells was sufficient to account for the rate of sorbitol formation in vivo. However, the enzyme was present in the highest amounts when the cells were grown on glucose alone, and it was repressed by the presence of fructose; this was not the case with the gluconolactonase.

Documentos Relacionados

• Hybrid neural network model for simulating sorbitol synthesis by glucose-fructose oxidoreductase in Zymomonas mobilis CP4
• Cloning, sequence analysis, and expression of the structural gene encoding glucose-fructose oxidoreductase from Zymomonas mobilis.
• Sorbitol promotes growth of Zymomonas mobilis in environments with high concentrations of sugar: evidence for a physiological function of glucose-fructose oxidoreductase in osmoprotection.
• Influence of high osmotic pressure on sorbitol production by Zymomonas mobilis
• Produção de sorbitol e ácidos orgânicos por Zymomonas mobilis