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Porphyrins combine readily with metals, coordinating with them in the central cavity. Iron, zinc, copper, nickel, and cobalt containing porphyrins are known, and many other metals can be inserted. A porphyrin in which no metal is inserted in its cavity is called a "free base".
Some iron containing porphyrins are called hemes, and heme-containing proteins, or hemoproteins, are found extensively in biochemistryBiochemistry is the chemistry of life. Biochemists study the elements, compounds and chemical reactions that are controlled by enzymes and take place in all living organisms. Biochemistry is focused on the structure and function of cellular components, su.
If one of the four pyrrole subunits is reduced, a chlorin is produced, the ring structure found in chlorophyllChlorophyll is the green photosynthetic pigment present in chloroplasts, which provides the energy necessary for photosynthesis. The intense green color of chlorophyll is due to its strong absorbence in the red and blue regions of the electromagnetic spec. If two of the four pyrrole subunits are reduced, then either a bacteriochlorin (as found in some photosynthetic bacteria), or an isobacteriochlorin, depending on the relative positions of the reduced pyrroles, is formed.
This is a schematic representation of porphyrin biosynthesis, with references by EC number and the OMIM database. The porphyriaThe porphyrias are inherited or acquired disorders of certain enzymes in the heme biosynthetic pathway (also called porphyrin pathway). They are broadly classified as hepatic porphyrias or erythropoetic porphyrias based on the site of the overproduction a associated with the deficiency of each enzyme is also shown:
| EnzymeAn enzyme is a protein, or protein complex, that catalyzes a chemical reaction. Like any catalyst, enzymes work by lowering the activation energy of a reaction, thus allowing the reaction to proceed to its steady state or completion much faster than it ot | SubstrateThe word substrate can mean the following: In biochemistry, a substrate is a molecule undergoing a reaction, for which the presence of an enzyme lowers the activation energy. The substrate binds with the enzyme's active site, and the enzyme provides an al | Product | Chromosome | EC | OMIM | porphyria |
| ALA synthase | Glycine, succinyl CoA | D-Aminolevulinic acid | 3p21.1 | 2.3.1.37 | 125290 | none |
| ALA dehydratase | D-Aminolevulinic acid | Porphobilinogen | 9q34 | 4.2.1.24 | 125270 | acute hepatic |
| PBG deaminase | Porphobilinogen | Hydroxymethyl bilane | 11q23.3 | 2.5.1.61 | 176000 | acute intermittent |
| Uroporphyrinogen III synthase | Hydroxymethyl bilane | Uroporphyrinogen III | 10q25.2-q26.3 | 4.2.1.75 | 606938 | congenital erythropoietic |
| Uroporphyrinogen III decarboxylase | Uroporphyrinogen III | Coproporphyrinogen III | 1q34 | 4.1.1.37 | 176100 | cutanea tarda |
| Coproporphyrinogen III oxidase | Coproporphyrinogen III | Protoporphyrinogen IX | 3q12 | 1.3.3.3 | 121300 | coproporphyria |
| Protoporphyrinogen oxidase | Protoporphyrinogen IX | Protoporphyrin IX | 1q22 | 1.3.3.4 | 600923 | variegate |
| Ferrochelatase | Protoporphyrin IX | Heme | 18q21.3 | 4.99.1.1 | 177000 | protoporphyria |