This test may be performed when porphyria or another disorder associated with an abnormal porphobilinogen (PBG) level is suspected.
PBG is a substance (enzyme) used by the body to make important substances such as the molecule call heme. Heme is a complex molecule that incorporates iron. The heme molecule is the oxygen carrying part of Hemoglobin found in red blood cells.
Various kinds of porphyrins exist with the same basic structure, but with slightly different chemical appearance. The major biochemical pathway includes several enzymatic conversions from the starting porphyrin molecule through several intermediates (delta-ALA, PBG, uroporphyrin, coproporphyrin, and protoporphyrin) to finally yield the end product, heme.
Each step requires the presence of an enzyme. If any of the enzymes are deficient (because of a genetic disease or inhibition by a toxic substance), a type of porphyria results.
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