BIOSYNTHESIS 



233 



CH3 



CH3— NCH2CH2OH 



/ 



CHa Choline 



CH, 



CHs— NCH2COO- 

 / 



CHa Glycine-betaine or trimethylglycine 



CH2SCH3 



I 



CHa 



I 

 CHNH2 



COOH 



Methionine 



S-adenosylmcchioninc 



S-adenosylhomocysteinc 



'%-CONH2 



nicotinamide 



-CONH2 



methylnicotinamide 



N 



I 



CHa 



HNCH2COOH 

 I 



C = NH guanidoacetic acid 



I 

 NHa 



CHa— NCH2COOH 



I 

 C = NH 



I 

 NH2 



creatine 



CH3>. 



^N— CH2-CH2OH 

 CH3 dimethylethanolaraine 



CHj 



^N-CHi-CHsOH 



CHa A^Tj choline 



t^ria 



Fig. 58 — Examples of transmethylation. 



