Lecture Notes

Amino acid breakdown
Learning objective:

1. Linkage between aa breakdown and the citric acid cycle
2. How breakdown of AA leads to creation of another AA
3. The process of methionine breakdown
4. Diseases that can result from the process of enzyme dysfunction
5. The process involved in phenylalanine/ tyrosine catabolism
6. The diseases (PKU) and the treatment there of in phenylalanine catabolism

Background information

 Nitrogen to urea
- Where does the carbon skeleton go?
Degraded into citric acid cycle components or their precursors
 AA breakdown creates new AA

LO1. LINKAGE OF AA BREAKDOWN INTO CITRIC ACID CYCLE

Glucogenic/ ketogenic AA

 20 AA with different breakdown pathways
 Glucogenic AA
- AA that can be converted to glucose through glycogenesis ( formation of glycogen from sugar)
- Breakdown to glucose precursors
Pyruvate
Α-ketoglutarate
Succinyl-Co-A
Fumerate
Oxaloacetate
- 13 AA

 Ketogenic AA
- Come from fatty acid breakdown
- AA that can be degraded directly into acetyl-coA, which is the precursor of ketone bodies.
- Break down to ketone bodies precursor
Acetyl-CoA (acetoacetyl-CoA)
- 2 AA (leucine & lysine)
 Glucogenic & ketogenic AA
- IIe
- Thr
- Phe
- Tyr
- Trp
 AA are heavily
lined to the citric
acid cycle

, Specifics- covered briefly

 AA that make
1. Pyruvate
- Alanine
- Cysteine
- Glycine
- Serine
- Threonine
- Include tryptophan, which makes alanine




2. Oxaloacetate
- Asparagine
- Aspartate
- Asparagine makes aspartate
3. Α-ketoglutamarate
- Arginine
- Glutamate
- Glutamine
- Histadine All to glutamate then to α-ketoglutamate
- Proline