154 



GENERAL BIOCHEMISTRY 



o O" 



.0^ CH2OPOPO- 



0_0 



HO OPO3H 



CH, 



CHoCCHOHCO 



CH3 



pantoic 

 acid 



NHCH2CH2CO 



;3-alanine 



■NHCH2CH2SH 



0-mercaptoethylamine 



V 



J 



pantothenic acid 



J 



coenzyme A 



where the dotted lines separate the overall structure into the com- 

 ponents named. The left-hand segment is a phosphate derivative of 

 adenosine diphosphate, ADP. Coenzyme A is acylated on the thiol 

 group as in 



CH3COCOO- + DPN+ + CoA 



pyruvic 

 dehvdroginase 



'- > 



other cofactors 

 (see page 171) 



CH3CO— CoA + CO2 + DPNH 



Thereafter, the acetyl group may be replaced by other acyl groups 

 or transferred to other substrates to form new types of materials, 

 as in the following: 



-OOCCH2COCOO- -f CH3CO— CoA + H2O .t 



oxalacetate 



citrogenase 



OH 



-OOCCH.CCHsCOO- + CoA 



I 

 COOH 



citrate 



Addition Enzymes 



This group might include all enzymes catalyzing any condensation 

 or combination of reactants. However, it is considered here to cover 

 only additions of water or ammonia to double bonds between carbon 

 atoms. Typical examples are: 



-OOCCH=CHCOO- + H2O ' -OOCCH2CHOHCOO- 



fumarate fumarase malate 



-OOCCH=CHCOO- + NH3 ± 



aspartase 



OOCCHoCHCOO- 



I 

 NH3+ 



aspartate 



