Open AccessThe Active Species of ‘CO 2 ’ Utilized by Reduced Ferredoxin: CO 2 Oxidoreductase from Clostridium pasteurianum
Author(s) -
THAUER Rudolf K.,
KÄUFER Barbara,
FUCHS Georg
Publication year - 1975
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1975.tb02143.x
Subject(s) - ferredoxin , formate , chemistry , oxidoreductase , dissociation constant , dissociation (chemistry) , reductase , inorganic chemistry , clostridium , enzyme , photochemistry , catalysis , biochemistry , biology , bacteria , receptor , genetics
Reduced ferredoxin: CO 2 oxidoreductase (CO 2 reductase) from Clostridium pasteurianum catalyzes the reduction of ‘CO 2 ’ to formate with reduced ferredoxin, an isotopic exchange between ‘CO 2 ’ and formate in the absence of ferredoxin, and the oxidation of formate to ‘CO 2 ’ with oxidized ferredoxin. The active species of ‘CO 2 ’, i.e. CO 2 or HCO 3 − (H 2 CO 3 ), utilized by the enzyme was determined. The method employed for the species identification was that of Cooper et al . (1968). Both ‘CO 2 ’ reduction to formate and the exchange reaction were studied. Data were obtained which are compatible with those expected if CO 2 is the active species. The V and the dissociation constant K s of the enzyme · CO 2 complex in dependence of pH were determined from initial velocity studies of the exchange reaction. V was found to be only slightly affected by pH between 5.5 and 7.5. K s was markedly dependent on pH; the constant increased with decreasing pH from 0.2 mM at pH 7.5 to 3 mM at pH 5.5.