Kinetic and spectroscopic analysis of the inactivating effects of nitric oxide on the individual components of Azotobacter vinelandii nitrogenase

Journal Article · Tue Mar 24 04:00:00 EST 1992 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00126a015· OSTI ID:5403378

Hyman, M R; Arp, D J ^[1]; Seefeldt, L C; Morgan, T V; Mortenson, L E ^[2]

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1. Oregon State Univ., Corvallis (United States)
2. Univ. of Georgia, Athens (United States)

The effect of nitric oxide (NO) on the individual components of Azotobacter vinelandii nitrogenase have been examined by kinetic and spectroscopic methods. Incubation of the Fe protein (Av2) for 1 h with stoichiometries of 4- and 8-fold molar excesses of NO to Av2 dimer resulted in a complete loss of activity of Av2 in C{sub 2}H{sub 2}-reduction assays. The kinetics of inactivation indicated that the minimum stoichiometry of NO to Av2 required to fully inactive Av2 lies between 1 and 2. The rate of inactivation of Av2 activity by NO was stimulated up to 2-fold by the presence of MgATP and MgADP but was unaffected by the presence of sodium dithionite. Unexpectedly, complete inactivation of Av2 by low ratios of NO to Av2 also resulted in a complete loss of its ability to bind MgATP and MgADP. UV-visible spectroscopy indicate that the effect of NO on Av2 involves oxidation of the (4Re-4S) center. EPR spectroscopy revealed that the loss of activity during inactivation of Av2 by NO correlated with the loss of the S = 1/2 and S = 3/2 signals. A correlation between UV-visible and EPR spectra features and the extent of NO inactivation has been established. The effects of NO on both nitrogenase components are interpreted in terms of the known reactivity of NO with Fe-S centers.

• DOE Contract Number: FG06-90ER20013
• OSTI ID: 5403378
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 31:11; ISSN 0006-2960; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550300* -- Cytology
59 BASIC BIOLOGICAL SCIENCES
AZOTOBACTER
BACTERIA
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
ENZYMES
INACTIVATION
KINETICS
METALLOPROTEINS
MICROORGANISMS
NITRIC OXIDE
NITRO-GROUP DEHYDROGENASES
NITROGEN COMPOUNDS
NITROGEN OXIDES
NITROGENASE
ORGANIC COMPOUNDS
OXIDATION
OXIDES
OXIDOREDUCTASES
OXYGEN COMPOUNDS
PROTEINS
REACTION KINETICS
SPECTRA
STOICHIOMETRY
ULTRAVIOLET SPECTRA