19.

In heme biosynthesis, the enzyme that introduces asymmetry to the orientation of pyrroles within the heme structure is

• a. delta-aminolevulinate synthetase.
• b. uroporphyrinogen III cosynthase.
• c. porphobilinogen deaminase.
• d. protoporphryinogen oxidase.
• e. uroporphrinogen III decarboxylase.