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Medical Term:

protoporphyrin type III

Pronunciation: pro'to-por'fi-rin

Definition: The principal protoporphyrin found in nature (one of 15 possible isomers), characterized by the presence of four methyl groups, two vinyl groups, and two propionic acid side chains; a porphyrin derivative that, with iron, forms the heme of hemoglobin and the prosthetic groups of myoglobin, catalase, cytochromes, etc.

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