In other species: pig

Categories: Homeostasis / metabolism phene

Links to possible relevant human trait(s) and/or gene(s) in OMIM: 125270 (gene) , 176000 (trait) , 176090 (trait) , 176200 (trait)

Mendelian trait/disorder: yes

Disease-related: yes

Key variant known: no

Cross-species summary: Porphyrins are a class of organic compounds characterised by four pyrrole nuclei connected in a ring structure. When combined with iron, porphyrins form haem, which is a component of haemoglobin, cytochromes, catalases and peroxidases. Thus, porphyrins are constituents of many compounds that play a vital role in biological systems. The biosynthesis of porphyrins involves a six-step process, starting with aminolaevulinic acid (ALA) and ending with protoporphyrin. Each step is catalysed by an enzyme. A deficiency of any one of these enzymes results in a buildup of intermediates prior to the step for which the enzyme is lacking, and a deficiency of intermediates after that step. In much of the literature, these intermediates are loosely called porphyrins. Porphyria is a general term for disorders resulting from a deficiency in any one of the enzymes in the porphyrin pathway, and a consequent buildup of intermediates (i.e. a buildup of porphyrins). Each enzyme deficiency gives rise to a distinct disorder. The six enzymes (in order), together with their deficiency disorders are: ALA dehydratase (Doss porphyria); porphobilinogen deaminase (Acute intermittent porphyria); urporphyrinogen II cosynthetase (Porphyria, congenital erythropoietic); uroporphyrinogen decarboxylase (Porphyria cutanea tarda); coproporphyrinogen III oxidase (Hereditary coproporphyria); protoporphyrinogen oxidase (Varigate porphyria). Some porphyrins are extemely photoreactive. Because of this, photosensitivity is a clinical sign of some of these disorders. Another major common clinical sign is haemolytic anaemia, due to a deficiency of haemoglobin. In some cases, the buildup of porphyrins results in a characteristic red staining of teeth, bones and urine.