FCH 532 Lecture 25. Chapter 26: Amino acid metabolism Quiz Friday Glucogenic/Ketogenic amino acids (15 min) Quiz Monday April 2:Translation factors Exam 3 on Monday, April 9. Figure 32-45 Translational initiation pathway in E. coli. 50S and 30S associated.
Chapter 26: Amino acid metabolism
Quiz Friday Glucogenic/Ketogenic amino acids (15 min)
Quiz Monday April 2:Translation factors
Exam 3 on Monday, April 9.
RF-2 = UAA and UGA
Cannot bind if EF-G is present.
RF-3-GTP binds to RF1 after the release of the polypeptide.
Hydrolysis of GTP on RF-3 facilitates the release of RF-1 (or RF-2).
EF-G-GTP and ribosomal recycling factor (RRF)-bind to A site. Release of GDP-RF-3
EF-G hydrolyzes GTP -RRF moves to the P site to displace the tRNA.
RRF and EF-G-GDP are released yielding inactive 70S
1. Tryptophan-2,3-dioxygenase, 2. Formamidase, 3. Kynurenine-3-monooxygense, 4. kynureninase (PLP dependent)
6. Amino carboxymuconate semialdehyde decarboxylase
7. Aminomuconate semialdehyde dehydrogenase
8. Hydratase, 9. Dehydrogense 10-16. Reactions 5-11 in lysine degradation.
1 and 2: activation of the enzyme’s BH4 and Fe(II) cofactors to yield pterin-4a-carbinolamine and a reactive oxyferryl [Fe(IV)=O2-]
3: Fe(IV)=O2- reacts with Phe to form an epoxide across the 3,4 bond.
4: epoxide opening to form carbocation at C3
5: migration of hydride from C4 to C3 to form more stable carbocation.
6: ring aromatization to form Tyr
Electrons are transferred from NADPH to FAD at active site 1 on the subunit to yield FADH2.
Electrons transferred from FADH2 to FMN on site 2 to yield FMNH2.
Gln is hydrolyzed to -glutamate and ammonia on site 3 of the subunit.
Ammonia is transferred to site 2 to form -iminoglutarate from -KG
-iminoglutarate is reduced by FMNH2 to form glutamate.
C-terminal domain of glutamate synthase is a 7-turn, right-handed helix.
43 angstrom long.
Structural role for the passage of ammonia.
Figure 26-55a X-Ray structure of S. typhimurium glutamine synthetase. (a) View down the 6-fold axis showing only the six subunits of the upper ring.
Active sites shown w/ Mn2+ ions (Mg2+)
Adenylation site is indicated in yellow (Tyr)
ADP is shown in cyan and phosphinothricin is shown (Glu inhibitor)