Redox regulation of glucose dehydrogenase from cells of the facultatively heterotrophic cyanobacterium Nostoc sp. strain MAC

András Juhász, Vilmos Csizmadia, György Borbély, János Udvardy

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Abstract

A glucose dehydrogenase (d-glucose:NAD(P)+ 1-oxidoreductase, EC 1.1.1.118(9)) was purified over 1100-fold, to near homogeneity, from Nostoc sp. strain MAC cells. The general enzymatic properties of the Nostoc enzyme were similar to those of the NAD(P)-dependent glucose dehydrogenase isolated earlier from facultatively heterotrophic cyanobacteria, heterotrophic bacteria and liver cells. In this work, we show that Nostoc glucose dehydrogenase can be modulated by various redox systems. Reducing agents such as dithiothreitol, cysteine and 2-mercaptoethanol decreased the activity of the enzyme. Reduced glutathione and ascorbic acid exerted only slight influence. The oxido-reductive modulation proved to be reversible. Treatment of the reduced glucose dehydrogenase with oxidants such as H2O2, Fe3+-EDTA and a Fe3+-chelate (Udvardy, J.; Borbély, Gy., Juhász, A.; and Farkas, G.L. (1984) FEBS Lett. 172, 11-16) reversed the process of deactivation. The range of the reductive deactivation depended on pH, being the most effective in the alkaline range. Addition of 10 mM Mg2+ and Ca2+ in the cuvette to the reduced form of glucose dehydrogenase, however, reactivated the enzyme. These cations had little effect on the oxidized enzyme. Mg2+ and Ca2+ changed the kinetic parameters (Km and Vmax) of the reduced, but not of the oxidized form of the Nostoc glucose dehydrogenase. Redox modulation was not accompanied by any change in the apparent molecular mass (110-120 kDa).

Original languageEnglish
Pages (from-to)119-127
Number of pages9
JournalBiochimica et Biophysica Acta (BBA)/Protein Structure and Molecular
Volume916
Issue number1
DOIs
Publication statusPublished - Nov 5 1987

Keywords

  • (Nostoc)
  • Cyanobacterium
  • Redox modulation
  • d-Glucose dehydrogenase

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology

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