METABOLIC BIOCHEMISTRY
Summer 2005
Lecture 6
August 12, 2005
LNC Chapter 16
The Citric Acid Cycle
Krebs CycleTCA Cycle
From G. Perkins, C. Renken, M.E. Martone,S.J. Young, M. Ellisman, and T. Frey
Outer membraneInner membrane
Intermembrane spaceMatrix
Pyruvate dehydrogenase as seen by electronmicroscopy
E. coli enzyme:
Mass > 4.5x106
24 copies of transacetylase (E2)
24 copies of pyruvate dehydrogenase (E1)
12 copies of dihydro-lipoyl dehydrogenase
Pyruvate + CoASH + NAD+ acetyl-CoA + CO2 + NADH
LNC 16.3
Coenzyme A
LNC 16.14
Lipoamide
LNC Fig. 13-18
FAD/FMN
FADH2/FMNH2
Figure from previous edition of LNC
TCA CYCLEKrebs cycleCitric acid
cycle
LNC 16.11
Products from one turn of the Krebs cycle
C4
C4
C4
C4
C6
C2
C5
C4
C6
LNC 16.8
Citrate Synthase
open form without substrates
closed from with substrates bound
oxaloacetate: yellowacetyl-coA: red
LNC 16.9 Iron-sulfur center in aconitase
Stereospecificity of the aconitase reaction
with citrate
LNC Fig.16.7
the only membrane-bound enzyme in the TCA cycle
LNC Fig.16.18
regulatory molecules:
NADHATP, ADPCa+2
key allosteric enzymes:
the dehydrogenasescitrate synthase
LNC Fig.16.15 the Krebs cycle is amphibolic
THE GLYOXYLATE CYCLE
LNC Chapter 16, pages 623-626
LNC Fig.16-20 Note that the figure 16-16 in the 3rd edition has an error(there is an O instead of an H)
C6
C6
C4
C4
C4C2C2
C2
from oxidation of fatty acids
End of lecture 6August 12, 2005