Porphyrins

Porphyrins (Greek "porphyra" purple dye) are organic-chemical dyes consisting of four pyrrole rings (tetrapyrrole). All nucleated cells are able to synthesize the porphyrin ring with the help of 4 enzymes (5-ALS synthase, 5-ALS dehydratase, porphobilinogen-desaminase and uroporphyrinogen-III-cosynthase). The simplest representative is porphin.

Porphyrins or porphyrin-related compounds form the basic chemical structures in chlorophyll and haem, in the protein haemoglobin built up on the haem and the various cytochromes.

Due to their ability to absorb electromagnetic radiation and to make the stored energy available for subsequent reactions, they mediate the use of sunlight for photosynthesis in chlorophyll, for example. Furthermore, they ensure the transport of oxygen in blood and tissue by reversible binding of oxygen in hemo- or myoglobin. Haem enzymes such as NOSynthases, cyclooxygenases, peroxidases, catalases, tryptophanpyrrolases and cytochromes catalyze complex biochemical reactions.

In chlorophyll, magnesium is the central ion anchored in the porphyrin ring. In heme it is the iron. In erythropoiesis, iron (besides erythropoietin) is the decisive factor in the regulation of heme synthesis.

Porphyrins are determined from urine: 20 ml from 24-hour urine collected, store away from light, always indicate the volume of the 24-hour urine. Determination by HPLC.

Standard values:

• Uroporphyrin: < 33 µg/24 hrs.
• Pentaporphyrin: < 5 µg/24 hrs.
• Hexaporphyrin: < 7 µg/24 hrs.
• Heptaporphyrin: < 10 µg/24 hrs
• Coproporphyrin: < 120 µg/24 hrs
• Porphobilinogen: 0.5-7.5 µmol/24 hrs. (ITC method).