Chapter 23: Amino Acid Synthesis Flashcards
Describe how proteins get ubiquitinated (know what each enzyme does, E1, E2, and E3).
-covalently attached to the damaged protein.
-C-term glycine gets bonded to the side chain NH2 of lysine.
E1: ubiquitin activating enzyme.
E2: transfers the Ub-AMP (active) to E2 cysteine.
E3: binds protein to be degraded and E2-Ub. It has multiple ubiquitin to protein.
Describe the importance of the amino terminal residue, give an example of one stabilizing
residue and one destabilizing residue.
The amino terminal residue is important because the E3 enzyme can recognize the residues to determine whether it should be ubiquinated or not and how fast it should be ubiquitinated.
Stabilizing: V (valine)
Destabilizing: H (histidine)
Describe what the two subunits of the Proteosome do.
Catalytic:
Once inside, the catalytic unit hydrolyzes the ‘target’ protein into amino acids.
Regulatory:
1. Recognize (bind to) ubiquinated proteins
2. hydrolyze off ubiquitin (Ub is reused)
3. Unfolds the ‘targeted’ protein and allows it to enter the catalytic subunit of the proteasome.
Know the typical 1st step of amino acid degradation.
The first step is to remove the nitrogen from the amino acid.
Describe the glucose-alanine cycle and its value.
In starvation conditions, ammonium + pyruvate will form alanine in the muscle.
From the muscle, the alanine will enter the bloodstream and then enter the liver.
In the liver, Alanine + alpha-ketoglutarate–> pyruvate + glutamate.
-The pyruvate can then be put into gluconeogenesis to produce glucose.
The value is that the nitrogen produced from breakdown of muscle can be removed and funneled into alanine and that can be produced to form more glucose in the liver from pyruvate.
Know the structure of carbamoyl phosphate and Describe how carbamoyl phosphate is made .
First carboxyphosphate is made and the carbamic acid and then from addition of one phosphate, carbamoyl phosphate is formed.
Know the names, structures and enzymes of the Urea Cycle.
Know what is meant by ketogenic and glucogenic amino acids.
Glucogenic: The amino acid breaks down into glucose precursors like pyruvate.
Ketogenic: The amino acid breaks down into a ketone body precursor like acetyl CoA or straight into acetoacetyl CoA.
Know which two amino acids are strictly ketogenic.
Lysine and Leucine.
Know the 7 possible fates of carbon atoms from the amino acids.
Oxaloacetate, pyruvate, 3PG, PEP, E-4-P, alpha-ketoglutarate and R-5-P.
