<p>An evidence describes the source of an annotation, e.g. an experiment that has been published in the scientific literature, an orthologous protein, a record from another database, etc.</p>
Protein involved in the synthesis of porphyrins which are compounds that contain the porphin structure, e.g. four pyrrole rings connected by methine bridges in a cyclic configuration to which a variety of side chains are attached. Porphyrins often chelate metal ions (Fe, Mg, Co, Zn, Cu, Ni). Examples are, heme proteins (which contain iron porphyrins) like myoglobin, hemoglobin, cytochromes, or related macrocycles including chlorophylls (which have a central magnesium ion) and pheophytins (which are metal free) and vitamin B-12 (which has cobalt).