439 



Pyrroles, Porphyrins and Related Compounds 



A = -CHuCOOH 

 P = -CH;CH:COOH 



Bogorad found'' that the enzyme porphobilinogen de- 

 aminase converts porphobilinogen (A) to uroporphyrino- 

 gen (D). Because a second enzyme, uroporphyrinogen 

 isomerase, has as its only substrate (not D) a product of 

 the action of porphobilinogen deaminase on (A), there 

 must have been one or more colorless intermediates. The 

 intermediates must be convertible, spontaneously or under 

 the continuing influence of porphobihnogen deaminase. 



1' Lawrence Bogorad, /. Biol. Chem. 233 501, 510, 516 (1958). 



