The final step in the coproporphyrin-dependent (CPD) heme biosynthesis pathway involves the oxidative decarboxylation of coproheme. The reaction is catalyzed by the enzyme coproheme decarboxylase (ChdC) and requires two equivalents of peroxide to complete the synthesis of one b-type heme molecule. At the present time, the CPD pathway appears to be limited to gram positive bacteria, many of them pathogenic, and the precise mechanism appears to differ between Firmicutes and Actinobacteria, thus underscoring the importance of understanding the function of ChdCs from multiple organisms. The reaction involves two subsequent oxidative decarboxylations and proceeds via the intermediate monovinyl monopropionate deuteroheme (MMD). Previous studies have provided evidence that the MMD intermediate does not leave the active site, and is instead rotated by ninety degrees, prior to binding another equivalent of peroxide and initiating another oxidative decarboxylation. Therefore, the mechanism necessitates a high degree of specificity to distinguish substrate from the MMD intermediate and product. To provide new insight into this selectivity, we report biochemical and structural data for the wild-type ChdC from Streptomyces coelicolor (ScChdC) and probe the importance of structurally conserved elements in the active site. Specifically, we provide evidence that a conserved elements of an active helix influence the transient state kinetics as well as the structural dynamics of an active site loop, with the latter playing a key role in enzyme specificity.