93 



Carotenes and Carotenoids 



Carotenes 



Sterols, Triterpenes, etc. 



cofactors 



CH3 



HOOC— CH2— C— CH2— CH2OH 



I 

 OH 



Mevalonic Acid 



± TPNH 

 CH3 



HOOC— CH2— C— CH2— CHO 



I 

 OH 



Mevaldic Acid 



Y 



± TPNH, DPNH 

 CH3 O 



-> HOOC— CH2— C— CH2— C— S— CoA 



condensing 

 enzyme 



OH 



/3-Hydroxy-/3-methyl- 



glutaryl-CoA (HMG-CoA) 



HMG 



cleavage 



enzyme 



CH3— C— S— CoA 

 Acetyl-CoA 



CH3— C— CHo— C— OH 

 Acetoacetic Acid 



succinyl CoA 



transferase 



(ATP activation) 



CH3— C— CH2— C— S— CoA + CoA— SH 

 Acetoacetyl CoA 



Fatty Acids 



The precursors of the carotenes are colorless, more reduced 

 compounds. These substances then are dehydrogenated in a 

 stepwise fashion, a process which requires light and oxygen. 



