(Catalytic mechanism of hydrogenase from aerobic N sub 2 -fixing microorganisms)
The results of this DOE-sponsored project have contributed to our understanding of the catalytic mechanism of A. vinelandii hydrogenase. A group of inhibitors have been characterized. These provide information about the different types of redox clusters involved in catalysis and the roles of each. One group has already used acetylene in a study of three desulfovibrian hydrogenases and shown that only the NiFe hydrogenases are inhibited. We have characterized a number of spectral properties of A. vinelandii hydrogenase. The EPR signals associated with this hydrogenase in the reduced state are reminiscent of other NiFe dimeric hydrogenases such as A. eutrophus, but distinctly difference from others such as D. gigas and Chromatium vinosum. Thus, while the NiFe dimeric hydrogenases are now recognized as a large group of similar enzymes, there are differences in the spectral and catalytic properties which are not explained by their similar redox inventories, identical subunit structures, immunological cross reactivity and conserved sequences. The inhibitors we have characterized are also proving of value in the spectral characterizations. Surprisingly, we only see a significant EP signal attributable to Ni after the enzyme has been inactivated with O{sub 2} and then reduced (though not reactivated). No spectral perterbations (EPR or UV-V is) of active enzyme can be attributed to binding of H{sub 2}, even though H{sub 2} clearly binds to this form of the enzyme. Acetylene, which does not substantially perterb the EPR signal of active hydrogenase, does result in a new absorption envelope in the UV-V is spectrum. Overall, the results of this project have revealed the complex interactions of the redox clusters in catalysis through studies of inhibitor mechanisms and spectral properties. 14 refs., 9 figs.
- Research Organization:
- California Univ., Riverside, CA (United States). Dept. of Biochemistry
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG03-84ER13257
- OSTI ID:
- 6145175
- Report Number(s):
- DOE/ER/13257-T2; ON: DE92003395
- Country of Publication:
- United States
- Language:
- English
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(Catalytic mechanism of hydrogenase from aerobic N sub 2 -fixing microorganisms)
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HYDROGENASES
BIOCHEMICAL REACTION KINETICS
ENZYME ACTIVITY
ENZYME INHIBITORS
ACETYLENE
AZOTOBACTER
CATALYSIS
CYANIDES
ELECTRON SPIN RESONANCE
ENZYME REACTIVATION
LIGANDS
METALLOPROTEINS
NITRIC OXIDE
NITROGEN FIXATION
OXYGEN
PROGRESS REPORT
SUBSTRATES
ULTRAVIOLET SPECTRA
VISIBLE SPECTRA
ALKYNES
BACTERIA
CHALCOGENIDES
DOCUMENT TYPES
ELEMENTS
ENZYMES
HYDROCARBONS
KINETICS
MAGNETIC RESONANCE
MICROORGANISMS
NITROGEN COMPOUNDS
NITROGEN OXIDES
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXIDOREDUCTASES
OXYGEN COMPOUNDS
PROTEINS
REACTION KINETICS
RESONANCE
SPECTRA
550200* - Biochemistry
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