437 



Pyrroles, Porphyrins and Related Compounds 



The photosynthetic bacteria, grown aerobically in light, 

 are a rich source, and so are corynebacteria. Part of the 

 biosynthetic pathway to the porphyrins has been explored 

 in photosynthetic bacteria, and it is thought to be of gen- 

 eral significance:^^' ^- 



-CO. 



HOOC— CH>— CH>— C— COOH 

 a-Ketoglutaric Acid 



-^ HOOC— CH.— CHo— CO— CoA 

 Succinyl Coenzyme A 



HOOC— CHo— CHo— CO— CoA + HOOC— CH2 

 Succinyl Coenzyme A Glycine 



-NH, 



-COo 



COOH 



HOOC— CH2— CHo— C— CHo— NH2 

 6-Aminolevulinic Acid 



H2N— CH2 



Pyridoxal phosphate is required as a co-factor (glycine 

 activator) in the glycine-succinyl-COA condensation.^^ 

 Porphobihnogen then condenses to form coproporphyrin 

 and protoporphyrin. In certain photosynthetic bacteria, 



" June Lascelles, Biochem. }. 62 78 (1956); idem., Abstracts of the 

 Gordon Conference on Metabolism, 1957. 



^- Goro Kikuchi, Abhaya Kumar, Phyllis Talmadge and David 

 Shemin, /. Biol. Chem. 233 1214 (1958). 



