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1.The Nitrogen Cycle
2.Amino Acid Biosynthesis
3.Urea Cycle
4.Amino Acid Catabolism
5.Molecules Derived from Amino Acid
(from Lehninger P873- 882)
Page 810
The Nitrogen Cycle
nitrite
Nitrite reductase
nitrate
Page 812
Nitrogen Fixation Is by Nitrogenase Complex
Page 815
The Fate of Ammonium
Three major reactions in all cells:
1.Carbamoyl-phosphate synthetase I
NH4+ +HCO3- +2ATPcarbamoyl-phosphate +2ADP+Pi +2H+
2.Glutamate dehydrogenase
3.Glutamine synthetase
The Glutamate Dehydrogenase Reaction
Page 815
The enzymatic reaction catalyzed by glutamine synthetase
Page 815
The Major Pathways of Ammonium Assimilation
Lead to Glutamine Synthesis
Page 816
Two principal pathways :
1. The GDH/GS pathway
2.GS/GOGAT in organisms confronting N limitation
(GOGAT is glutamate synthase or glutamate:oxoglutarate amino transferase)
The GDH/GS Pathway of Ammonium Assimilation
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GDH: glutamate dehydrogenase
GS: glutamine synthetase
The GS/GOGAT Pathway of Ammonium Assimilation
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The Subunit Organization of Bacterial Glutamine Synthetase
Page 818
Page 817,818 & 820
Glutamine Synthetase (GS) in E. coli is regulated in three
ways:
1.Feedback inhibition
2.Covalent modification (interconverts between inactive
and active forms)
3.Regulation of gene expression
Allosteric Regulation of Glutamine Synthetase by
Feedback Inhibition
Page 819
Covalent Modification of GS: Adenylylation of Tyr397 in the
Glutamine Synthetase
Page 819
The Covalent Modification of GS
Page 820
Gene Expression Regulates GS
Page 820
Amino Acids Are Formed from a-keto Acids by
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Transamination
Human Dietary Requirements for Amino Acids
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Amino Acid Biosynthesis
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Synthesis of Amino Acids in Bacteria
Chapter 25
1
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Page 816 & 824
Page 825
Urea cycle
arginine
2
Page 822 & 831
See page 831
Page 830
Page 830
3
Pyruvate + glutamateAlanine + a-KG
Page 822
See P835 & P836
4
Page 822
Page 837
The Synthesis of S-adenosylmethionine (SAM) From Methionine
Page 833
The Synthesis of S-adenosylmethionine (SAM) From Methionine
Page 833
5
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Page 843
(also called
Phenylalanine
hydroxylase)
Some of the Aromatic Compounds Derived from Chorismate
Page 841
Some of the Aromatic Compounds Derived from Chorismate
Page 840
Page 842
Histidine Biosynthesis and Purine Biosynthesis Are Connected by Common
Intermediate
Page 840 & 844
The Urea Cycle
Page 827
Argininosuccinate
synthetase
Orithine
transcarbamoylase
Argininosuccinase
arginase
Alanine Transports Ammonia from Muscles to the Liver
The TCA Cycle and Urea Cycle Can Be linked
Amino Acid Biosynthesis Inhibitors as Herbicides
Page 838
*uncompetitive & noncompetitive inhibitor
Overview of the Catabolism of Amino Acids in Mammals
Page 840
Metabolic Degradation of the Common Amino Acids
Page 841 & 845
*glucogenic amino acid
*ketogenic amino acid
Asn
Page 845
Page 848
Page 849
Maple syrup urine disease (楓漿尿病)
Page 849
Page 850
Page 850
*Phenylketonuria(苯丙酮尿症)
Page 843 & 848
(phenylalanine
hydroxylase)
Phenylalanine + a-KG
Aspatame
transaminase
Phenylpyruvate + glutamate
*Alkaptonuria (黑尿症)
Page 850
Homogentisate
dioxygenase
*Maple syrup urine disease (楓漿尿病) (page 846)
*Alkaptonuria (黑尿症)(page 848)
*Phenylketonuria(苯丙酮尿症)(page 848)
1.Ammonotelic
2.Ureotelic
3.Uricotelic
Page 850
Biomolecules Derived from Amino Acid (from
Lehninger P873- 882)
Page 854 & 855
1.Porphyrins
Page 855
Aged erythrocyte
Page 856
Jaundice 黄疸
2.Creatine
Page 858
3.Glutathione
Page 858
Page 858
4.Neurotransmitters
Page 859 & 860
4.Polyamines
Page 860 & 861
5.Nitric Oxide
Page 860 & 861
Soluble Guanylyl Cyclases Are Receptors for Nitric Oxide
Stripped away
(sildenafil)
Viagra 威而鋼
phosphodiesterase
GMP