Congenital Erythropoeitic Porphyria ( Cep )

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The UROS Gene &
Congenital Erythropoeitic Porphyria

Zachary T. Hall
BIOL 301 – 005
October 23, 2014 Introduction Congenital Erythropoeitic Porphyria (CEP), originally called congenital hepatoporphyria (also known as Gunther’s Disease), is the rarest form of a group of uniquely distinct autosomally inherited disorders first classified and discovered by German physician Hans Gunther in the first decade of the twentieth century. Due to its relatively new discovery and rarity, CEP does not have a lengthy history. However, the disease has been historically associated with clinical manifestations including extreme cutaneous photosensitivity, osteopenia, scarring, blistering, corneal ulceration, red urinal discoloration,
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URO-synthase is an enzyme involved in the metabolism of the tetrapyrrole compound porphyrin, which composes heme. Heme performs a variety of biological functions but is most commonly known for being a component of hemoglobin, helping it to provide oxygen to tissues throughout the body. Specifically, URO-synthase functions to convert a linear chain of four porphobilinogen molecules, hydroxymethylbilane (HMB), into the first metabolic intermediate in the biosynthesis of heme, the cyclic tetrapyrrole uroporphyrinogen III [3, 4]. This conversion of hydroxymethylbilane by URO-synthase into uroporphyrinogen III (URO-III) is necessary to facilitate the continuation of the pathway and the successful production of heme. URO-synthase performs this function primarily within the mitochondria and cytoplasm of erythrocyte precursor cells in bone marrow, although the liver also functions to produce heme by the same biosynthetic pathway [5]. CEP has been linked to a variety of loss of function mutations on the UROS gene including missense, nonsense, splice-site and small intragenic deletions. However the majority of these mutations occur so rarely that the most common pathogenic mutations are considered to be missense mutations, specifically a C to T change at nucleotide 197, substituting an alanine for valine at residue 66 (A66V) and a T to C change at nucleotide 217, substituting a cysteine to arginine
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