Kreb's TCA Cycle reactions and structures

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Citrate synthase

Structural diagram for citrate synthase reaction

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Aconitase

Aconitase reaction structures

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Isocitrate DH

Isocitrate DH reaction including structures

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mainline Sequence

generalized diagram for mainline sequence reactions

 

 

 

 

 

 

 

 

 

 

 

 

 

 

aerobic glucose metabolism pathway diagram including compartmentation

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

* In some tissues (insect flight muscle, fast twitch muscle) the reducing equivalents of NADH must be pumped against a gradient at a cost of 1 ATP (it is used to make FADH2).

 Reaction
Energy Product

factor
ATP Equivalents
(@2.5 ATP/NAD)
ATP Equivalents
(@3 ATP/NAD)
Glycolysis
 Hexokinase
ADP

1 x -1

- 1
-1 
 PFK
ADP

1 x-1

- 1
 -1
 GA-3-P DH
NADH

2 x 2.5 (1.5)*

5 (3)*
6 (4)*
PGA Kinase
ATP

2 x1

2
 2
Pyruvate Kinase
ATP

2 x 1

2
 2
 Pyruvate DH Complex & Kreb's Cycle
Pyruvate DH Complex
NADH

2 x 2.5

5
 6
Isocitrate DH
NADH

2 x 2.5

5
2-oxoglutarate DH Complex
NADH

2 x 2.5

5
 6
Succinyl-CoA Synthetase
GTP

2 x 1

2
Succinate DH
FADH2

2 x 1.5

3
 4
Malate DH
NADH

2 x 2.5

5
 6

  TOTAL=

32 (30)*
 38 (36)*

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Kreb's Cysle intermediate catabolism pathway diagram

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Data from E. A. Newsholme and A. R. Leach Biochemistry for the Medical Sciences. John Wiley & Sons, New York (1983) pp 101 & 110.

 Enzyme Substrate Substrate Conc. (mM)  Km (mM) DeltaG (kJ/mol)  Effectors
 Citrate synthase acetyl-CoA 100-600 5-10 -53.9
Succinyl CoA (-), ATP (-), NADH (-)
oxaloacetate 1-10 5-10
 Isocitrate DH (NAD+) isocitrate 150-700 50-200 -17.5
 Ca2+ (+), ATP (-), ADP(+), NADH (-)
 2-Oxoglutarate DH 2-oxoglutarate 600-5900 60-200 -43.9
 Ca2+ (+), Succinyl CoA (-), NADH (-)

 

 

Last modified 5 April 2010