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Porphyrias: A diverse group of metabolic diseases characterized by errors in the biosynthetic pathway of HEME in the LIVER, the BONE MARROW, or both. They are classified by the deficiency of specific enzymes, the tissue site of enzyme defect, or the clinical features that include neurological (acute) or cutaneous (skin lesions). Porphyrias can be hereditary or acquired as a result of toxicity to the hepatic or erythropoietic marrow tissues.Porphyrias, Hepatic: A group of metabolic diseases due to deficiency of one of a number of LIVER enzymes in the biosynthetic pathway of HEME. They are characterized by the accumulation and increased excretion of PORPHYRINS or its precursors. Clinical features include neurological symptoms (PORPHYRIA, ACUTE INTERMITTENT), cutaneous lesions due to photosensitivity (PORPHYRIA CUTANEA TARDA), or both (HEREDITARY COPROPORPHYRIA). Hepatic porphyrias can be hereditary or acquired as a result of toxicity to the hepatic tissues.Porphyria, Acute Intermittent: An autosomal dominant porphyria that is due to a deficiency of HYDROXYMETHYLBILANE SYNTHASE in the LIVER, the third enzyme in the 8-enzyme biosynthetic pathway of HEME. Clinical features are recurrent and life-threatening neurologic disturbances, ABDOMINAL PAIN, and elevated level of AMINOLEVULINIC ACID and PORPHOBILINOGEN in the urine.Porphyria, Erythropoietic: An autosomal recessive porphyria that is due to a deficiency of UROPORPHYRINOGEN III SYNTHASE in the BONE MARROW; also known as congenital erythropoietic porphyria. This disease is characterized by SPLENOMEGALY; ANEMIA; photosensitivity; cutaneous lesions; accumulation of hydroxymethylbilane; and increased excretion of UROPORPHYRINS and COPROPORPHYRINS.Porphyria, Variegate: An autosomal dominant porphyria that is due to a deficiency of protoporphyrinogen oxidase (EC 1.3.3.4) in the LIVER, the seventh enzyme in the 8-enzyme biosynthetic pathway of HEME. Clinical features include both neurological symptoms and cutaneous lesions. Patients excrete increased levels of porphyrin precursors, COPROPORPHYRINS and protoporphyrinogen.Porphyria Cutanea Tarda: An autosomal dominant or acquired porphyria due to a deficiency of UROPORPHYRINOGEN DECARBOXYLASE in the LIVER. It is characterized by photosensitivity and cutaneous lesions with little or no neurologic symptoms. Type I is the acquired form and is strongly associated with liver diseases and hepatic toxicities caused by alcohol or estrogenic steroids. Type II is the familial form.Hydroxymethylbilane Synthase: An enzyme that catalyzes the tetrapolymerization of the monopyrrole PORPHOBILINOGEN into the hydroxymethylbilane preuroporphyrinogen (UROPORPHYRINOGENS) in several discrete steps. It is the third enzyme in the 8-enzyme biosynthetic pathway of HEME. In humans, deficiency in this enzyme encoded by HMBS (or PBGD) gene results in a form of neurological porphyria (PORPHYRIA, ACUTE INTERMITTENT). This enzyme was formerly listed as EC 4.3.1.8PorphobilinogenUroporphyrinogen Decarboxylase: An enzyme that catalyzes the decarboxylation of UROPORPHYRINOGEN III to coproporphyrinogen III by the conversion of four acetate groups to four methyl groups. It is the fifth enzyme in the 8-enzyme biosynthetic pathway of HEME. Several forms of cutaneous PORPHYRIAS are results of this enzyme deficiency as in PORPHYRIA CUTANEA TARDA; and HEPATOERYTHROPOIETIC PORPHYRIA.Protoporphyrinogen Oxidase: A membrane-bound flavoenzyme that catalyzes the oxygen-dependent aromatization of protoporphyrinogen IX (Protogen) to protoporphyrin IX (Proto IX). It is the last enzyme of the common branch of the HEME and CHLOROPHYLL pathways in plants, and is the molecular target of diphenyl ether-type herbicides. VARIEGATE PORPHYRIA is an autosomal dominant disorder associated with deficiency of protoporphyrinogen oxidase.Porphyrins: A group of compounds containing the porphin structure, four pyrrole rings connected by methine bridges in a cyclic configuration to which a variety of side chains are attached. The nature of the side chain is indicated by a prefix, as uroporphyrin, hematoporphyrin, etc. The porphyrins, in combination with iron, form the heme component in biologically significant compounds such as hemoglobin and myoglobin.Uroporphyrinogen III Synthetase: An enzyme that catalyzes the cyclization of hydroxymethylbilane to yield UROPORPHYRINOGEN III and water. It is the fourth enzyme in the 8-enzyme biosynthetic pathway of HEME, and is encoded by UROS gene. Mutations of UROS gene result in CONGENITAL ERYTHROPOIETIC PORPHYRIA.Uroporphyrins: Porphyrins with four acetic acid and four propionic acid side chains attached to the pyrrole rings.Porphyria, Hepatoerythropoietic: An autosomal recessive cutaneous porphyria that is due to a deficiency of UROPORPHYRINOGEN DECARBOXYLASE in both the LIVER and the BONE MARROW. Similar to PORPHYRIA CUTANEA TARDA, this disorder is caused by defects in the fifth enzyme in the 8-enzyme biosynthetic pathway of HEME, but is a homozygous enzyme deficiency with less than 10% of the normal enzyme activity. Cutaneous lesions are severe and mutilating.Coproporphyrins: Porphyrins with four methyl and four propionic acid side chains attached to the pyrrole rings. Elevated levels of Coproporphyrin III in the urine and feces are major findings in patients with HEREDITARY COPROPORPHYRIA.5-Aminolevulinate Synthetase: An enzyme of the transferase class that catalyzes condensation of the succinyl group from succinyl coenzyme A with glycine to form delta-aminolevulinate. It is a pyridoxyal phosphate protein and the reaction occurs in mitochondria as the first step of the heme biosynthetic pathway. The enzyme is a key regulatory enzyme in heme biosynthesis. In liver feedback is inhibited by heme. EC 2.3.1.37.Coproporphyria, Hereditary: An autosomal dominant porphyria that is due to a deficiency of COPROPORPHYRINOGEN OXIDASE in the LIVER, the sixth enzyme in the 8-enzyme biosynthetic pathway of HEME. Clinical features include both neurological symptoms and cutaneous lesions. Patients excrete increased levels of porphyrin precursors, 5-AMINOLEVULINATE and COPROPORPHYRINS.Uroporphyrinogens: Porphyrinogens which are intermediates in heme biosynthesis. They have four acetic acid and four propionic acid side chains attached to the pyrrole rings. Uroporphyrinogen I and III are formed from polypyrryl methane in the presence of uroporphyrinogen III cosynthetase and uroporphyrin I synthetase, respectively. They can yield uroporphyrins by autooxidation or coproporphyrinogens by decarboxylation.Aminolevulinic Acid: A compound produced from succinyl-CoA and GLYCINE as an intermediate in heme synthesis. It is used as a PHOTOCHEMOTHERAPY for actinic KERATOSIS.Porphyrinogens: Colorless reduced precursors of porphyrins in which the pyrrole rings are linked by methylene (-CH2-) bridges.Levulinic Acids: Keto acids that are derivatives of 4-oxopentanoic acids (levulinic acid).Hexachlorobenzene: An agricultural fungicide and seed treatment agent.Porphobilinogen Synthase: An enzyme that catalyzes the formation of porphobilinogen from two molecules of 5-aminolevulinic acid. EC 4.2.1.24.Ammonia-Lyases: Enzymes that catalyze the formation of a carbon-carbon double bond by the elimination of AMMONIA. EC 4.3.1.FlavoproteinsFerrochelatase: A mitochondrial enzyme found in a wide variety of cells and tissues. It is the final enzyme in the 8-enzyme biosynthetic pathway of HEME. Ferrochelatase catalyzes ferrous insertion into protoporphyrin IX to form protoheme or heme. Deficiency in this enzyme results in ERYTHROPOIETIC PROTOPORPHYRIA.Heme: The color-furnishing portion of hemoglobin. It is found free in tissues and as the prosthetic group in many hemeproteins.Griseofulvin: An antifungal agent used in the treatment of TINEA infections.Coproporphyrinogen Oxidase: An enzyme that catalyzes the oxidative decarboxylation of coproporphyrinogen III to protoporphyrinogen IX by the conversion of two propionate groups to two vinyl groups. It is the sixth enzyme in the 8-enzyme biosynthetic pathway of HEME, and is encoded by CPO gene. Mutations of CPO gene result in HEREDITARY COPROPORPHYRIA.Coproporphyrinogens: Porphyrinogens which are intermediates in the heme biosynthesis. They have four methyl and four propionic acid side chains attached to the pyrrole rings. Coproporphyrinogens I and III are formed in the presence of uroporphyrinogen decarboxylase from the corresponding uroporphyrinogen. They can yield coproporphyrins by autooxidation or protoporphyrin by oxidative decarboxylation.Dicarbethoxydihydrocollidine: 1,4-Dihydro-2,4,6-trimethyl-3,5-pyridinedicarboxylic acid diethyl ester.Skin DiseasesOxidoreductases Acting on CH-CH Group Donors: A subclass of enzymes which includes all dehydrogenases acting on carbon-carbon bonds. This enzyme group includes all the enzymes that introduce double bonds into substrates by direct dehydrogenation of carbon-carbon single bonds.Protoporphyria, Erythropoietic: An autosomal dominant porphyria that is due to a deficiency of FERROCHELATASE (heme synthetase) in both the LIVER and the BONE MARROW, the last enzyme in the 8-enzyme biosynthetic pathway of HEME. Clinical features include mainly neurological symptoms, rarely cutaneous lesions, and elevated levels of protoporphyrin and COPROPORPHYRINS in the feces.Photosensitivity Disorders: Abnormal responses to sunlight or artificial light due to extreme reactivity of light-absorbing molecules in tissues. It refers almost exclusively to skin photosensitivity, including sunburn, reactions due to repeated prolonged exposure in the absence of photosensitizing factors, and reactions requiring photosensitizing factors such as photosensitizing agents and certain diseases. With restricted reference to skin tissue, it does not include photosensitivity of the eye to light, as in photophobia or photosensitive epilepsy.Bloodletting: Puncture of a vein to draw blood for therapeutic purposes. Bloodletting therapy has been used in Talmudic and Indian medicine since the medieval time, and was still practiced widely in the 18th and 19th centuries. Its modern counterpart is PHLEBOTOMY.Protoporphyrins: Porphyrins with four methyl, two vinyl, and two propionic acid side chains attached to the pyrrole rings. Protoporphyrin IX occurs in hemoglobin, myoglobin, and most of the cytochromes.Allylisopropylacetamide: An allylic compound that acts as a suicide inactivator of CYTOCHROME P450 by covalently binding to its heme moiety or surrounding protein.Precipitating Factors: Factors associated with the definitive onset of a disease, illness, accident, behavioral response, or course of action. Usually one factor is more important or more obviously recognizable than others, if several are involved, and one may often be regarded as "necessary". Examples include exposure to specific disease; amount or level of an infectious organism, drug, or noxious agent, etc.Hemochromatosis: A disorder of iron metabolism characterized by a triad of HEMOSIDEROSIS; LIVER CIRRHOSIS; and DIABETES MELLITUS. It is caused by massive iron deposits in parenchymal cells that may develop after a prolonged increase of iron absorption. (Jablonski's Dictionary of Syndromes & Eponymic Diseases, 2d ed)Erythrocytes: Red blood cells. Mature erythrocytes are non-nucleated, biconcave disks containing HEMOGLOBIN whose function is to transport OXYGEN.Liver Diseases: Pathological processes of the LIVER.Carboxy-Lyases: Enzymes that catalyze the addition of a carboxyl group to a compound (carboxylases) or the removal of a carboxyl group from a compound (decarboxylases). EC 4.1.1.