Biological Molecules that require Nitrogen
- Amino Acids
- Amino Sugars
- Complex Polysaccharides
Describe the aminotransferase reactions
- The first step in amino acid degradation
- Using Pyroxidal phosphate (B6) as a cofactor, they remove the amino group and give it to the corresponding alpha-keto acid.
Glutamate + alpha-keto acid
alpha-ketoglutarate + Glutamate
Aspartate + A-ketoglutarate
Oxaloacetate + Glutamate
Alanine + A-ketoglutarate
Pyruvate + Glutamate
Name this molecule:
Vitamin B6 (pyroxidal)
Name this Molecule:
For which types of reactions is pyroxidal phosphate a prosthetic group?
- Transamination reactions
- Chemical change at alpha, beta, or gamma carbons of common amino acids
- Some decarboxylation reactions
- Deamination (Ser ---> pyruvate + NH3)
Excrete ammonia into water because it is water soluble
Ammonia is converted to urea in the liver by the urea cycle
Convert ammonia to uric acid; precipitates and can be excreted without water
Birds and Reptiles
Describe how nitrogen can travel through the blood to the liver
- In most tissues, ammonia is convered to glutamine using glutamine synthetase, then transported through the blood to the liver.
- Muscle uses the glucose-alanine cycle, wherein pyruvate undergoes transamination w/glutamate to form alanine and A-ketoglutarate. Alanine is then transported to the liver.
Describe the Glucose-Alanine Cycle
Pyruvate undergoes transamination with glutamate, which forms alanine and A-ketoglutarate. Alanine is then transported to the liver.