Peptidase propeptide and YPEB domain likely has a protease inhibitory function (Yeats et al., 2004), whereas non-COPD-associated Uroporphyrinogen decarboxylase (UROD), a branch point enzyme in the biosynthesis of tetrapyrroles, catalyzes the decarboxylation of four acetate groups of uroporphyrinogen III, resulting in coproporphyrinogen III playing an essential role in the biosynthesis of heme and chlorophyll, a protein family already characterized in yeasts and Bacillus subtilis (Garey et al., 1992; Hansson and Hederstedt, 1992). Here, UROD is linked to chronic obstructive pulmonary disease.