II GLUCOSE, FATTY ACIDS CATABOLISM 



TPN* 



a) Glucose-6-phosphate > 6-phosphogluconic acid 



TPN" 



b) 6-Phosphogluconic » ribulose-5-phosphate + CO2 (carbon atom i of glucose) 



c) Ribulose-5-P ' ' xylulose-5-P 



transketolase 



d) Xylulose-5-P + ribose-5-P ' sedoheptulose-7-P + glyceraldehyde-3-P 



transaldolase 



e) Sedoheptulose-7-P + glyceraldehyde-3-P '■ fructose-6-P + erythrose-P 



f ) Fructose-6-P ^ ' glucose-6-phosphate 



Repeat steps a,b,c) glucose-6-P -^ xylulose-j-P + CO2 (carbon atom 2 of glucose) 



transketolase 



g) Xylulose-5-P + erythrose-P ' r fructose-6-P + glyceraldehyde-P 



Repeat steps f,a,b) fructose-6-P -^ ribulose-5-P + CO2 (carbon atom 3 of glucose) 

 h) Ribulose-5-P ' ribose-5-phosphate 



Sum : glucose-6-P + (ribose-5-P) -^ 3 CO2 + glyceraldehyde-P + (ribose-5-phosphate) 



J. The oxidation of pyruvate to acetyl-CoA 



Under aerobic conditions, pyruvate may be oxidized to acetyl-CoA. Four vitamins 

 are involved in this transformation, thiamine, lipoic acid, niacin, and pantothenic 

 acid (Horecker and Mehler, 1955; Hager and Gunsakis, 1953). The mechanism 

 is shown in Fig. 2. 



O 



CH,— -C — COOH + CH2— CHp— CH— (CH2)4 — CO — Thiamine pyrophosphate 

 I I 



s ■ s 



CO2 + CHj— CH2-CH — (CH2)4 — CO— Thiamine pyrophosphote 



S 5H 



I 



c=o 



I 



CHo CoA SH 



CH,— C-S — CoA + CH2—CH2—CH — (CH2)4 — CO — Thiamine pyrophosphate 



I I 



Acetyl -CoA cu 51-1 



Reduced lipothiamide pyrophosphate 

 DPN'^ 



H'^ + DPNH + CH2—CH2-CH-(CH2)4— CO— Thiamine pyrophosphate 

 I I 



S S 



Fig. 2. Formation of acetyl-CoA from pyruvate. 



Literature p. 124 



