ESPM 131 Lecture Notes - Lecture 21: Tropospheric Ozone, Ozone Depletion, Glutamine
14 May 2018
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Lecture 21: Nitrogen
●Primary limiting nutrient in terr ecosystems, essential for life, transformation linked to C
●Increased use of N fert and cult of N-fixing crops has increased reactive N (NH3/NO3) in
soil/water
●Nitrous oxide (NO2) : GHG, stratospheric ozone depletion
●Nitric oxide (NO) : tropospheric ozone production
●Mineralization/immobilization:
○Mineralization : org N to mineral N (NH4 and NO3) to be used by plants
■GDH for mineralization as well (op direction)
■Deamination occurs when organism needs C-skel to metabolize for E
○Immobilization : mineral N (NH4) to organic N, 2 pathways
1. Reductive amination (GDH) into glutamate, important at high NH4
a. [ A-keto glutarate, e-s, and ammonium → glutamate]
2. Enzymes: important at lower ammonium conc
a. Glutamine synthase (GS) : glutamate and ammonium to glutamine
i. Afin for NH4 higher than GDH, requires ATP
ii. Inhibited by N-containing compounds (NH4)
iii. Under elaborate control
b. Glutamate synthase (GOGAT ): glutamine and A-keto g to 2 glutamate
i. Ketoglutarate enzyme
●Transamination : glutamate + pyruvate to alanine (other C-skeletons)
●Soil control:
○Decomp community’s requirement for N relative to C (C/N of decomp), usually 10/1
○Decomp community’s C-use eficiency (to cells vs CO2) 40% is v eficient
○Quality (N content) of substrate and how long it’s been decomp (C/N of material/rounds)
■Plant material w/ high C/N → net immobilization
■Plant material w/ low C/N → net mineralization , usually 15-30/1
■As plant material decomps, the C/N increases
■C constipation : in forests w/ high C/N, can’t decomp debris b/c of low N
■Microbes may be used as “N banks”
○Break point: neither net mineralization or immobilization
○Major points:
■As plant material decomposes, the C/N decreases
■Plant w/ high C/N → immob
■Plant w/ low C/N → mineralization
■Rate of decomp will be afected by avail of N in plant and soil
●Ureases : hydrolyze urea, prod NH4
○Nucleic acids 2nd to proteins in N-substrate importance
○Major product of decomp of purine/pyrimidines to urea, H+ consumption
●Fates of ammonium: Localized increase in pH can be important (volatilization of NH3, equil
pushed forward)
○Taken up by plants
○Assimilated by microbes
Document Summary
P(cid:418)ima(cid:418)(cid:482) limitin(cid:322) nut(cid:418)ient in te(cid:418)(cid:418) e(cid:283)os(cid:482)stems, essential (cid:321)o(cid:418) li(cid:321)e, t(cid:418)ans(cid:321)o(cid:418)mation linked to c. In(cid:283)(cid:418)eased use o(cid:321) n (cid:321)e(cid:418)t and (cid:283)ult o(cid:321) n- (cid:481)in(cid:322) (cid:283)(cid:418)ops has in(cid:283)(cid:418)eased (cid:418)ea(cid:283)ti(cid:475)e n (cid:1827)nh(cid:1682)/no(cid:1682)(cid:1828) in soil/(cid:476)ate(cid:418) Nit(cid:418)ous o(cid:481)ide (cid:1827)no2(cid:1828) : ghg, st(cid:418)atosphe(cid:418)i(cid:283) ozone depletion. Nit(cid:418)i(cid:283) o(cid:481)ide (cid:1827)no(cid:1828) : t(cid:418)oposphe(cid:418)i(cid:283) ozone p(cid:418)odu(cid:283)tion. Mine(cid:418)alization : o(cid:418)(cid:322) n to mine(cid:418)al n (cid:1827)nh(cid:1683) and no(cid:1682)(cid:1828) to (cid:282)e used (cid:282)(cid:482) plants. Gdh (cid:321)o(cid:418) mine(cid:418)alization as (cid:476)ell (cid:1827)op di(cid:418)e(cid:283)tion(cid:1828) Deamination o(cid:283)(cid:283)u(cid:418)s (cid:476)hen o(cid:418)(cid:322)anism needs c-skel to meta(cid:282)olize (cid:321)o(cid:418) e. Immo(cid:282)ilization : mine(cid:418)al n (cid:1827)nh(cid:1683)(cid:1828) to o(cid:418)(cid:322)ani(cid:283) n, (cid:1681) path(cid:476)a(cid:482)s (cid:1680). Redu(cid:283)ti(cid:475)e amination (cid:1827)gdh(cid:1828) into (cid:322)lutamate, impo(cid:418)tant at hi(cid:322)h nh(cid:1683) a. [ a-keto (cid:322)luta(cid:418)ate, e-s, and ammonium (cid:322)lutamate] (cid:1681). Enz(cid:482)mes: impo(cid:418)tant at lo(cid:476)e(cid:418) ammonium (cid:283)on(cid:283: glutamine s(cid:482)nthase (cid:1827)gs(cid:1828) : (cid:322)lutamate and ammonium to (cid:322)lutamine i. ii. iii. A(cid:498) n (cid:321)o(cid:418) nh(cid:1683) hi(cid:322)he(cid:418) than gdh, (cid:418)e(cid:417)ui(cid:418)es atp. Glutamate s(cid:482)nthase (cid:1827)gogat (cid:1828): (cid:322)lutamine and a-keto (cid:322) to (cid:1681) (cid:322)lutamate i. T(cid:418)ansamination : (cid:322)lutamate + p(cid:482)(cid:418)u(cid:475)ate to alanine (cid:1827)othe(cid:418) c-skeletons(cid:1828)
