This entry represents uroporphyrinogen decarboxylase (HemE), which catalyzes the fifth step in the heme biosynthetic pathway, converting uroporphyrinogen III to coproporphyrinogen III by decarboxylating the four acetate side chains of the substrate [PMID:9564029]. This step takes the pathway toward protoporphyrin IX, a common precursor of both heme and chlorophyll, rather than toward precorrin 2 and its products.

This activity is essential in all organisms, and subnormal activity of URO-D leads to the most common form of porphyria in humans, porphyria cutanea tarda (PCT).