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Porphyria Educational Services


Porphyria Educational Services Weekly Bulletin
Vol. 2 No. 51 December 24, 2000
FOCUS: Understanding Porphyrins and Pyrroles

In the early days of understanding porphyria, one type, AIP, was called pyrroloporphyria.
The name came from the pyrroles which chain together to make up the porphyrins
which are the basis of porphyria.

Porphyrins are tetrapyrroles. They consist of four pyrrole rings joined by methene bridges. Such tetrapyrroles are considered weakly aromatic.

The porphyrins all bear certain names.

A porphyrin of interest will consist of a word and a number such as that of uroporphyrin III.
The word denotes the kinds of substituents found on the ring, and the number denotes how
they are arranged.

Ceratin elements can also be added. Take for instance the element of iron.

Iron can be added to protoporphyrin IX. The oxidation state of the iron ion and the identity of
the negatively charged counterion determine the name of the product.

When iron is added to the product, it then becomes heme.

If iron (III), or ferric iron, is added, the product is hemin if the counterion is chloride.
hematin if the counterion is hydroxide.

And what of porphyrinogens?

Porphyrinogens are more reduced than the corresponding porphyrins, so oxidation of a
porphyrinogen (pronounce) produces the corresponding porphyrin.

Many reactions occur in porphyrins. There are the enzymes, convertion, bondings, and
other changes that occur all around the tetrapyrrole ring.

There are no simplistic definitions for the chain of events that occurs. The study of porphyrins is most complex as are the class of diseases known as the porphyrias.

Judy Morrison, Ph.D.
Biochemistry