Nitrogen CycleNitrification>Oxidation of NH + to NO, (nitrite) then to NO, (nitrate)>Some microbes can fully oxidation to nitrate - some to only nitrite>Replenishes nitrites and nitrates in soilN2nitrogendenitrificationDenitrificationfixationnitrogenase>Conversion of NO3toN,>CompletesthecycleNOjNHNitratenitritenitratereductasereductasenitrificationnitrificationNONitrite
Nitrogen Cycle Nitrification Oxidation of NH4 + to NO2 _ (nitrite) then to NO3 _ (nitrate) Some microbes can fully oxidation to nitrate – some to only nitrite Replenishes nitrites and nitrates in soil Denitrification Conversion of NO3 _ to N2 Completes the cycle
Nitrogen fixation. The nitrogenase complex, which carries out this fundamentaltransformation, consists of two proteins: a reductase, which provideselectrons with high reducing power, and a nitrogenase, which uses theseelectrons to reduce N, to NH3The transfer of electrons from the reductase to the nitrogenase componentis coupled to the hydrolysis of ATP by the reductase.ElectronsfromreducedADPATPferredoxin+PReductaseNitrogenase(Fe protein)(MoFeprotein)
Nitrogen fixation • The nitrogenase complex, which carries out this fundamental transformation, consists of two proteins: a reductase, which provides electrons with high reducing power, and a nitrogenase, which uses these electrons to reduce N2 to NH3. • The transfer of electrons from the reductase to the nitrogenase component is coupled to the hydrolysis of ATP by the reductase
Nitrogen AssimilationNow that we have useful form of N (NH)>How does it get incorporated into biological molecules?> NH + toxic to cells (pH)Initial assimilation>Glutamine synthetase (synthetase uses an NTP)>Found inall organisms
Nitrogen Assimilation Now that we have useful form of N (NH3) How does it get incorporated into biological molecules? NH4 + toxic to cells (pH） Initial assimilation Glutamine synthetase (synthetase uses an NTP) Found in all organisms
Nitrogen AssimilationGlutamine synthetase (synthetase uses an NTP)> Glu first activated by phosphoryl transfer>NH,exchangedforP;>Activity is tightly regulated>Glnisacarrierofaminegroups>Glu + Gln → higher concentrations than other amino acidscOOADPcOOcooTPNH:H2HOPOTNH*NH,+NH,*NHyGlutamateGlutamine
Nitrogen Assimilation Glutamine synthetase (synthetase uses an NTP) Glu first activated by phosphoryl transfer NH2 exchanged for Pi Activity is tightly regulated Gln is a carrier of amine groups Glu + Gln → higher concentrations than other amino acids
NitrogenAssimilationInitial assimilation>In bacteria and plants> glutamate synthase (-ase not -tase, so no NTP needed)NADPHCOO-COO-COOCOOH.NHN-HH+NADP+HA-HHCH2CH2CH2H2glutamateCH2CHzCH2H2synthaseCOOCooCooNH22Glutamatea-KetoglutarateGlutamine>Gln synthetase (Glu→Gln)+Glu synthase (α-KG +Gln → 2 Glu)α-ketoglutarate+NH,++NADPH+ATP→Glu+NADP++ADP+P,>Mammals don't have Glu synthase (synthesized in other ways)
Nitrogen Assimilation Initial assimilation In bacteria and plants glutamate synthase (-ase not –tase, so no NTP needed) Gln synthetase (Glu → Gln) + Glu synthase (α-KG + Gln → 2 Glu) Mammals don’t have Glu synthase (synthesized in other ways)