Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Query: EC:1.12.7.2 (
hydrogenase
)
3,522
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Three genetically distinct, but structurally similar, isozymes of nitrogenase catalyze biological N
2
reduction to 2NH
3
: Mo-, V-, and Fe-nitrogenase, named respectively for the metal (
M
) in their active site metallocofactors (metal-ion composition,
M
Fe
7
). Studies of the Mo-enzyme have revealed key aspects of its mechanism for N
2
binding and reduction. Central to this mechanism is accumulation of four electrons and protons on its active site metallocofactor, called FeMo-co, as metal bound hydrides to generate the key E
4
(
4H)
("Janus") state. N
2
binding/reduction in this state is coupled to reductive elimination (
re
) of the two hydrides as H
2
, the forward direction of a reductive-elimination/oxidative-addition (
re/oa
) equilibrium. A recent study demonstrated that Fe-nitrogenase follows the same
re/oa
mechanism, as particularly evidenced by HD formation during turnover under N
2
/D
2
. Kinetic analysis revealed that Mo- and Fe-nitrogenases show similar rate constants for
hydrogenase
-like H
2
formation by hydride protonolysis (
k
HP
) but significant differences in the rate constant for H
2
re
with N
2
binding/reduction (
k
re
). We now report that V-nitrogenase also exhibits HD formation during N
2
/D
2
turnover (and H
2
inhibition of N
2
reduction), thereby establishing the
re/oa
equilibrium as a universal mechanism for N
2
binding and activation among the three nitrogenases. Kinetic analysis further reveals that differences in catalytic efficiencies do not stem from significant differences in the rate constant (
k
HP
) for H
2
production by the
hydrogenase
-like side reaction but directly arise from the differences in the rate constant (
k
re
) for the
re
of H
2
coupled to N
2
binding/reduction, which decreases in the order Mo > V > Fe.
...
PMID:Mo-, V-, and Fe-Nitrogenases Use a Universal Eight-Electron Reductive-Elimination Mechanism To Achieve N
2
Reduction. 3128 1
