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Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

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Page 1: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

Section M

Nitrogen metabolism1. Reduction of N2 into ammonia (NH3 or NH4

+)

2. Synthesis of the 20 amino acids.

3. Amino acid degradation

Page 2: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

M1 Nitrogen fixation and assimilation

The nitrogen cycle

Nitrogen fixation

Nitrogen assimilation

Page 3: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 4: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

The nitrogen in amino acids, purines, pyrimidines and other biomolecules ultimately comes from atmospheric nitrogen.

Cyanobacteria ( 蓝藻细菌 , photosynthetic) and rhizobia ( 根瘤菌 , symbiont) can fix N2 into NH3.

The reduction of N2 to NH3 is thermodynamically favorable :

N2 + 6e- + 6H+ 2NH3 G`o = -33.5kJ/mol

Page 5: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 6: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

Certain bacteria can fix N2 into ammonia

N2 + 6e- + 6H+ 2NH3 G`o = - 33.5kJ/mol

Page 7: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 8: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

The nitrogenase complex in certain bacteria catalyzes the conversion of N2 to NH3, which is the ultimate source of nitrogen for all the nitrogen-containing biomolec

ules.

Page 9: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

The nitrogenase complex consists of dinitrogenase and dinitrogenase redutase

ADP

ADP

4Fe-4S

4Fe-4S(P-cluster)

Fe-Mo cofactor e-?

Fe-Mo cofactor

4Fe-4S(P-cluster) 4Fe-4S

ADP

ADP

Page 10: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

Molybdenum

N2 is believed to be reduced at theFe-Mo cofactorN2

Fe

FeFe

Fe

FeFe Fe

SS

S

S

S

S

SSS

Mo

Page 11: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

Electrons are transferred through a series of carriers to N2 for its reduction on the nitrogenase co

mplexN2 + 8H+ +8e- + 16ATP + 16H2O

2NH3 + H2 + 16ADP +

16Pi

Page 12: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

Electrons are transferredto N2 bound in the active site of dinitrogenasevia ferredoxin/flavodoxin and dinitrogenasereductase

Page 13: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 14: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

Reduced nitrogen in the form of NH4

+ is assimilated into organic nitrogen-containing compounds by the action of glutamate dehydrogenase and glutamine synthet

ase .

Ammonia is incorporated into biomolecules through Glutamate and glutamine.

Page 15: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 16: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

glutamate dehydrogenase

Page 17: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

glutamine synthetase

Page 18: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

glutamine synthetase

Glutamate + NH3 +ATP Glutamine + ADP + Pi

Glutamine + Ketoglutarate 2Glutamate

NADPH NADP+

形成 Gln 既是氨同化的一种方式，又可消除过高氨浓度带来的毒害，还可以作为氨的供体，用于 Glu 的合成。

Page 19: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

M2 Amino acid metabolism

Page 20: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

The amino acids can be grouped into six biosynthetic families depending on the metabolic intermediate from which their carbon skeleton is derived.

Biosynthesis of amino acids

Page 21: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 22: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

The 20 amino acids are synthesized mainly from intermediates of glycolysis, citric acid cycle, or pentose phosphate pathway in bact

eria and plants.

Page 23: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 24: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 25: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 26: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 27: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 28: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 29: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 30: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 31: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 32: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 33: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 34: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 35: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 36: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 37: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 38: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 39: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 40: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 41: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 42: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 43: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 44: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 45: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 46: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 47: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 48: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 49: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 50: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 51: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 52: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 53: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 54: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 55: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 56: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 57: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 58: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 59: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 60: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 61: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 62: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 63: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 64: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 65: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 66: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 67: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 68: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 69: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 70: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 71: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 72: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 73: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 74: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 75: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 76: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 77: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 78: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

PEP

E – 4 – P莽草酸 分枝酸

色氨酸 苯丙氨酸 酪氨酸

Page 79: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 80: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 81: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 82: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

莽草酸

Page 83: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 84: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 85: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

分枝酸

Page 86: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 87: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 88: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 89: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 90: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 91: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 92: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

Only about half of the amino acids can be

synthesized by us human being: the rest have to be obtained from diet, thus called essential amino

acids.

Page 93: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 94: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

Amino Acids that can not be synthesized by

human (essentialAmino acids)

Histidine (Arg)

Isoleucine

Leucine

Lysine

Methionine (and/or cysteine)

Phenylalanine (and/or tyrosine)

Threonine

Tryptophan

Valine

Page 95: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

Amino acids are precursors of many specialized biomolecules

Page 96: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

Porphyrins in mammalsare made from Gly and succinyl-CoA.

Page 97: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

Amino acid degradation

Page 98: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

The surplus amino acids in animals can be completely

oxidized or converted to other storable fuels Amino acids in excess can neither be stored, nor excreted,

but oxidized to release energy or converted to fatty acids/glucose.

Animals utilize amino acids for energy generation following a protein meal, during starvation.

Microorganisms can also use amino acids as an energy source when the supply is in excess.

Plants almost never use amino acids (neither fatty acids) as an energy source.

Page 99: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

Dietary proteins are digested into amino acids via the action of pepsin, trypsin, chymotrypsin, carboxypeptidase and aminopepti

dase

Page 100: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

AminotransferaseAminotransferaseor transaminaseor transaminase

The The -amino group of many amino acids -amino group of many amino acids is transferred to is transferred to -ketoglutarate-ketoglutarate

via catalysis of a specificvia catalysis of a specific aminotransferaseaminotransferase,, producing producing GluGlu and an and an -keto acid.-keto acid.

This reaction is fully reversible!

Page 101: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 102: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

The major route for the deamination of amino acids is transamination followed by the oxidative deamination of glutamate. How ever, a minor route also exists that involves direct oxidation of the amino acid by L-amino acid oxidase.

Page 103: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

The carbon skeletons of the amino acids are converted

(funneled) into seven major metabolic intermediates before being completely

oxidized via the citric acid cycle

Page 104: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation
Page 105: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

Trp, Ala, Gly, Ser, Cys are convertedto pyruvate (thus being glucogenic)

Part of Trp, Phe, Tyr, Leu & Lys are converted to acetoacetyl-CoA, and Part of Trp, Leu, and Ile is converted to acetyl-CoA. (thus being ketogenic)

Page 106: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

Summary Atmospheric N2 is reduced to ammonia by the di

nitrogenase reductase and the dinitrogenase (containing a key Fe-Mo cofactor) of the nitrogenase complex present only in certain bacteria.

Ammonia enters organic molecules via Glu and Gln.

Glutamine amidotransferases catalyzes the transferring of the amide amino group to many acceptor molecules.

Page 107: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

Amino acids are mainly derived from intermediates of glycolysis, the citric acid cycle, and the pentose phosphate pathway.

Pro and Arg are derived from Glu, which is synthesized from -ketoglutarate.

Ser, Gly, and Cys are derived from 3-phosphoglycerate. Met and Thr are derived from oxaloacetate. Lys and Ile are derived from oxaloacetate and pyruvate.

Biosynthesis

Page 108: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

Val and Leu are derived from pyruvate. Ile and Val are derived from Thr/pyruvate and two molecul

es of pyruvate respectively, using the same enzymes; Leu is derived from two molecules of pyruvate, sharing four steps of reactions with Val synthesis.

Tryptophan is derived from phosphoenolpyruvate, erythrose 4-P, Gln, PRPP, and one Ser.

Phe and Tyr are synthesized from two phosphoenolpyruvates, one erythrose 4-P, and one Glu.

Page 109: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

Amino acid in excess can neither be stored, nor excreted, but oxidized or converted.

The amino groups and carbon skeletons of amino acids take separate but interconnected pathways.

Glutamate collects and delivers free ammonia. Gln and Glu releases NH4

+ in mitochondria.

Degradation

Page 110: Section M Nitrogen metabolism 1. Reduction of N 2 into ammonia (NH 3 or NH 4 + ) 2. Synthesis of the 20 amino acids. 3. Amino acid degradation

Some amino acids are converted to intermediates of citric acid cycle by simple removal of the amino groups.

Acetyl-CoA is formed from the degradation of many amino acids.

A few genetic diseases are related to defects of Phe catabolism enzymes.


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Application Note 201 Measuring Ammonia (NH3) With ... · 21 41 1 232 raesystems.com MEASURING AMMONIA (NH3) WITH . PHOTOIONIZATION DETECTORS. Ammonia (NH. 3) is a common alkaline

Carbon CompoundsSecure Site  · •All Amino acids have 3 functional groups and contain C, H, O and N •Carboxyl group (-COOH) •Amino group (-NH 2)) (portion of the amino acid

for Ammonia and NH 3 - Yellow Jacketyellowjacket.com/wp-content/uploads/2015/01/142884_Rev.C-English.pdffor Ammonia and NH 3 Systems ... the ballast allows fresh air to enter the pumping