porphyrin

SYN: porphin.

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por·phy·rin 'pȯr-fə-rən n any of various compounds with a structure that consists essentially of four pyrrole rings joined by four =CH- groups esp one (as chlorophyll or hemoglobin) containing a central metal atom and usu. having biological activity

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n.

one of a number of pigments derived from porphin, which are widely distributed in living things. All porphyrins form chelates with iron, magnesium, zinc, nickel, copper, and cobalt. These chelates are constituents of haemoglobin, myohaemoglobin, the cytochrome, and chlorophyll, and are thus important in many oxidation/reduction reactions in all living organisms. See also protoporphyrin IX.

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por·phy·rin (porґfə-rin) any of a group of compounds containing the porphin structure, four pyrrole rings connected by methylidyne (CH) bridges in a cyclic configuration, to which a variety of side chains may be attached. The nature of the side chains is indicated by a prefix, such as coproporphyrin, etioporphyrin, hematoporphyrin, mesoporphyrin, protoporphyrin, or uroporphyrin. Structural isomers are indicated by roman numerals. Free porphyrins are rarely found in tissues except in disorders of heme biosynthesis (porphyrias), but they do occur in the prosthetic groups of hemoglobin, myoglobin, and cytochromes, complexed with metal ions. The term is sometimes used to include porphin or to denote porphin specifically. See also porphyrinogen and chlorophyll.

Porphyrin. (A), Pyrrole ring; (B), porphin ring; (C), protoporphyrin IX.