(Catalytic mechanism of hydrogenase from aerobic N sub 2 -fixing microorganisms)

Technical Report · Tue Jan 01 04:00:00 EST 1991

DOI:https://doi.org/10.2172/6145175· OSTI ID:6145175

Arp, D J

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: DOE; 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

Related Subjects

550200* -- Biochemistry
550700 -- Microbiology
59 BASIC BIOLOGICAL SCIENCES
ACETYLENE
ALKYNES
AZOTOBACTER
BACTERIA
BIOCHEMICAL REACTION KINETICS
CATALYSIS
CHALCOGENIDES
CYANIDES
DOCUMENT TYPES
ELECTRON SPIN RESONANCE
ELEMENTS
ENZYME ACTIVITY
ENZYME INHIBITORS
ENZYME REACTIVATION
ENZYMES
HYDROCARBONS
HYDROGENASES
KINETICS
LIGANDS
MAGNETIC RESONANCE
METALLOPROTEINS
MICROORGANISMS
NITRIC OXIDE
NITROGEN COMPOUNDS
NITROGEN FIXATION
NITROGEN OXIDES
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXIDOREDUCTASES
OXYGEN
OXYGEN COMPOUNDS
PROGRESS REPORT
PROTEINS
REACTION KINETICS
RESONANCE
SPECTRA
SUBSTRATES
ULTRAVIOLET SPECTRA
VISIBLE SPECTRA