Topic
Hydroxymethylbilane
About: Hydroxymethylbilane is a research topic. Over the lifetime, 77 publications have been published within this topic receiving 2282 citations. The topic is also known as: (hydroxymethyl)bilane & 3,8,13,18-tetrakis(carboxymethyl)-5,10,15,22,23,24-hexahydro-19-(hydroxymethyl)-21H-biline-2,7,12,17-tetrapropanoic acid.
Papers published on a yearly basis
Papers
TL;DR: The treatment of choice for the acute hepatic porphyrias is intravenous heme therapy, which repletes a critical regulatory heme pool in hepatocytes and leads to downregulation of hepatic ALA synthase, which is a biochemical hallmark of all forms of acute porphyria in relapse.
Abstract: Porphyrins and metalloporphyrins are the key pigments of life on earth as we know it, because they include chlorophyll (a magnesium-containing metalloporphyrin) and heme (iron protoporphyrin). In eukaryotes, porphyrins and heme are synthesized by a multistep pathway that involves eight enzymes. The first and rate-controlling step is the formation of delta-aminolevulinic acid (ALA) from glycine plus succinyl CoA, catalyzed by ALA synthase. Intermediate steps occur in the cytoplasm, with formation of the monopyrrole porphobilinogen and the tetrapyrroles hydroxymethylbilane and a series of porphyrinogens, which are serially decarboxylated. Heme is utilized chiefly for the formation of hemoglobin in erythrocytes, myoglobin in muscle cells, cytochromes P-450 and mitochondrial cytochromes, and other hemoproteins in hepatocytes. The rate-controlling step of heme breakdown is catalyzed by heme oxygenase (HMOX), of which there are two isoforms, called HMOX1 and HMOX2. HMOX breaks down heme to form biliverdin, carbon monoxide, and iron. The porphyrias are a group of disorders, mainly inherited, in which there are defects in normal porphyrin and heme synthesis. The cardinal clinical features are cutaneous (due to the skin-damaging effects of excess deposited porphyrins) or neurovisceral attacks of pain, sometimes with weakness, delirium, seizures, and the like (probably due mainly to neurotoxic effects of ALA). The treatment of choice for the acute hepatic porphyrias is intravenous heme therapy, which repletes a critical regulatory heme pool in hepatocytes and leads to downregulation of hepatic ALA synthase, which is a biochemical hallmark of all forms of acute porphyria in relapse.
195 citations
174 citations
TL;DR: Porphobilinogen deaminase isolated from Escherichia coli is shown to contain a dipyrromethane cofactor (DPMC) linked covalently to the enzyme, which is involved in the binding of intermediates during the catalytic reaction but is not incorporated into the product preuroporphyrinogen.
153 citations
TL;DR: High levels of enzymatic activity and immunoreactive protein were expressed when a blunt-ended 971-base-pair Ava II cDNA fragment containing the entire coding region was inserted into vectors for expression in Escherichia coli.
Abstract: Uroporphyrinogen III synthase [URO-synthase; hydroxymethylbilane hydro-lyase (cyclizing), EC 4.2.1.75], the fourth enzyme in the heme biosynthetic pathway, is responsible for conversion of the linear tetrapyrrole, hydroxymethylbilane, to the cyclic tetrapyrrole, uroporphyrinogen III. The deficient activity of URO-synthase is the enzymatic defect in the autosomal recessive disorder congenital erythropoietic porphyria. To facilitate the isolation of a full-length cDNA for human URO-synthase, the human erythrocyte enzyme was purified to homogeneity and 81 nonoverlapping amino acids were determined by microsequencing the N terminus and four tryptic peptides. Two synthetic oligonucleotide mixtures were used to screen 1.2 x 10(6) recombinants from a human adult liver cDNA library. Eight clones were positive with both oligonucleotide mixtures. Of these, dideoxy sequencing of the 1.3 kilobase insert from clone pUROS-2 revealed 5' and 3' untranslated sequences of 196 and 284 base pairs, respectively, and an open reading frame of 798 base pairs encoding a protein of 265 amino acids with a predicted molecular mass of 28,607 Da. The authenticity of this clone was established by colinearity of the predicted amino acid sequence with 81 microsequenced residues from the purified enzyme. In addition, high levels of enzymatic activity and immunoreactive protein were expressed when a blunt-ended 971-base-pair Ava II cDNA fragment containing the entire coding region was inserted into vectors for expression in Escherichia coli. The isolation and expression of this full-length cDNA for human URO-synthase should facilitate studies of the structure, organization, and chromosomal localization of this heme biosynthetic gene as well as the characterization of the molecular lesions causing congenital erythropoietic porphyria.
100 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 4 |
| 2018 | 2 |
| 2015 | 1 |
| 2014 | 1 |
| 2013 | 2 |
| 2012 | 1 |