2 research outputs found
MOESM1 of Oleaginous yeast platform for producing biofuels via co-solvent hydrothermal liquefaction
Additional file 1. Supplementary HTL data and experimental information
Evidence That the P<sub>i</sub> Release Event Is the Rate-Limiting Step in the Nitrogenase Catalytic Cycle
Nitrogenase
reduction of dinitrogen (N<sub>2</sub>) to ammonia
(NH<sub>3</sub>) involves a sequence of events that occur upon the
transient association of the reduced Fe protein containing two ATP
molecules with the MoFe protein that includes electron transfer, ATP
hydrolysis, P<sub>i</sub> release, and dissociation of the oxidized,
ADP-containing Fe protein from the reduced MoFe protein. Numerous
kinetic studies using the nonphysiological electron donor dithionite
have suggested that the rate-limiting step in this reaction cycle
is the dissociation of the Fe protein from the MoFe protein. Here,
we have established the rate constants for each of the key steps in
the catalytic cycle using the physiological reductant flavodoxin protein
in its hydroquinone state. The findings indicate that with this reductant,
the rate-limiting step in the reaction cycle is not protein–protein
dissociation or reduction of the oxidized Fe protein, but rather events
associated with the P<sub>i</sub> release step. Further, it is demonstrated
that (i) Fe protein transfers only one electron to MoFe protein in
each Fe protein cycle coupled with hydrolysis of two ATP molecules,
(ii) the oxidized Fe protein is not reduced when bound to MoFe protein,
and (iii) the Fe protein interacts with flavodoxin using the same
binding interface that is used with the MoFe protein. These findings
allow a revision of the rate-limiting step in the nitrogenase Fe protein
cycle