ISSN:
1432-1327
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract An air-stable formate dehydrogenase, an enzyme that catalyzes the oxidation of formate to CO2, was purified from a sulfate-reducing organism, Desulfovibrio desulfuricans ATCC 27774. The enzyme has a molecular mass of approximately 150 kDa (three different subunits: 88, 29 and 16 kDa) and contains three types of redox-active centers: four c-type hemes, nonheme iron arranged as two [4Fe-4S]2+/1+ centers and a molybdenum-pterin site. Selenium was also chemically detected. The enzyme specific activity is 78 units per mg of protein. Mo(V) EPR signals were observed in the native, reduced and formate-reacted states. EPR signals related to the presence of multiple low-spin hemes were also observed in the oxidized state. Upon reduction, an examination of the EPR data under appropriate conditions distinguishes two types of iron-sulfur centers, an [Fe-S] center I (g max=2.050, g med=1.947, g min=1.896) and an [Fe-S] center II (g max=2.071, g med=1.926, g min=1.865). Mössbauer spectroscopy confirmed the presence of four hemes in the low-spin state. The presence of two [4Fe-4S]2+/1+ centers was confirmed, one of these displaying very small hyperfine coupling constants in the +1 oxidation state. The midpoint redox potentials of the enzyme metal centers were also estimated.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s007750050125
Permalink