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Molecular Genetics and Metabolism Nov 20195-Aminolevulinate (ALA) synthase (ALAS), a homodimeric pyridoxal-5'-phosphate (PLP)-dependent enzyme, catalyzes the first step of heme biosynthesis in metazoa, fungi and... (Review)
Review
5-Aminolevulinate (ALA) synthase (ALAS), a homodimeric pyridoxal-5'-phosphate (PLP)-dependent enzyme, catalyzes the first step of heme biosynthesis in metazoa, fungi and α-proteobacteria. In this review, we focus on the advances made in unraveling the mechanism of the ALAS-catalyzed reaction during the past decade. The interplay between the PLP cofactor and the protein moiety determines and modulates the multi-intermediate reaction cycle of ALAS, which involves the decarboxylative condensation of two substrates, glycine and succinyl-CoA. Substrate binding and catalysis are rapid, and product (ALA) release dominates the overall ALAS kinetic mechanism. Interconversion between a catalytically incompetent, open conformation and a catalytically competent, closed conformation is linked to ALAS catalysis. Reversion to the open conformation, coincident with ALA dissociation, defines the slowest step of the reaction cycle. These findings were further substantiated by introducing seven mutations in the16-amino acid loop that gates the active site, yielding an ALAS variant with a greatly increased rate of catalytic turnover and heightened specificity constants for both substrates. Recently, molecular dynamics (MD) simulation analysis of various dimeric ALAS forms revealed that the seven active site loop mutations caused the proteins to adopt different conformations. In particular, the emergence of a β-strand in the mutated loop, which interacted with two preexisting β-strands to form an anti-parallel three-stranded β-sheet, conferred the murine heptavariant with a more stable open conformation and prompted faster product release than wild-type mALAS2. Moreover, the dynamics of the mALAS2 active site loop anti-correlated with that of the 35 amino acid C-terminal sequence. This led us to propose that this C-terminal extension, which is absent in prokaryotic ALASs, finely tunes mammalian ALAS activity. Based on the above results, we extend our previous proposal to include that discovery of a ligand inducing the mammalian C-terminal extension to fold offers a good prospect for the development of a new drug for X-linked protoporphyria and/or other porphyrias associated with enhanced ALAS activity and/or porphyrin accumulation.
Topics: 5-Aminolevulinate Synthetase; Biosynthetic Pathways; Catalysis; Heme; Humans; Kinetics; Molecular Dynamics Simulation; Protein Conformation; Pyridoxal Phosphate; Substrate Specificity
PubMed: 31345668
DOI: 10.1016/j.ymgme.2019.06.003 -
Hepatology (Baltimore, Md.) Sep 2014Porphyrias are a group of eight metabolic disorders, each resulting from a mutation that affects an enzyme of the heme biosynthetic pathway. Porphyrias are classified as... (Review)
Review
UNLABELLED
Porphyrias are a group of eight metabolic disorders, each resulting from a mutation that affects an enzyme of the heme biosynthetic pathway. Porphyrias are classified as hepatic or erythropoietic, depending upon the site where the gene defect is predominantly expressed. Clinical phenotypes are classified as follows: (1) acute porphyrias with neurovisceral symptoms: acute intermittent porphyria; delta amino-levulinic acid hydratase deficiency porphyria; hereditary coproporphyria; and variegate porphyria and (2) cutaneous porphyrias with skin blistering and photosensitivity: porphyria cutanea tarda; congenital erythropoietic porphyria; hepatoerythropoietic porphyria and both erythropoietic protoporphyrias: autosomal dominant and X-linked. Liver transplantation (LT) may be needed for recurrent and/or life-threatening acute attack in acute intermittent porphyria or acute liver failure or end-stage chronic liver disease in erythropoietic protoporphyria. LT in acute intermittent porphyria is curative. Erythropoietic protoporphyria patients needing LT should be considered for bone marrow transplantation to achieve cure.
CONCLUSION
This article provides an overview of porphyria with diagnostic approaches and management strategies for specific porphyrias and recommendations for LT with indications, pretransplant evaluation, and posttransplant management.
Topics: Humans; Liver Transplantation; Porphyrias
PubMed: 24700519
DOI: 10.1002/hep.27086 -
The Journal of Biological Chemistry Mar 2022Heme is a critical biomolecule that is synthesized in vivo by several organisms such as plants, animals, and bacteria. Reflecting the importance of this molecule,... (Review)
Review
Heme is a critical biomolecule that is synthesized in vivo by several organisms such as plants, animals, and bacteria. Reflecting the importance of this molecule, defects in heme biosynthesis underlie several blood disorders in humans. Aminolevulinic acid synthase (ALAS) initiates heme biosynthesis in α-proteobacteria and nonplant eukaryotes. Debilitating and painful diseases such as X-linked sideroblastic anemia and X-linked protoporphyria can result from one of more than 91 genetic mutations in the human erythroid-specific enzyme ALAS2. This review will focus on recent structure-based insights into human ALAS2 function in health and how it dysfunctions in disease. We will also discuss how certain genetic mutations potentially result in disease-causing structural perturbations. Furthermore, we use thermodynamic and structural information to hypothesize how the mutations affect the human ALAS2 structure and categorize some of the unique human ALAS2 mutations that do not respond to typical treatments, that have paradoxical in vitro activity, or that are highly intolerable to changes. Finally, we will examine where future structure-based insights into the family of ALA synthases are needed to develop additional enzyme therapeutics.
Topics: 5-Aminolevulinate Synthetase; Aminolevulinic Acid; Anemia, Sideroblastic; Animals; Genetic Diseases, X-Linked; Heme; Humans; Structure-Activity Relationship
PubMed: 35093382
DOI: 10.1016/j.jbc.2022.101643 -
JAMA Dermatology Feb 2023Erythropoietic protoporphyria (EPP) is a rare and underdiagnosed genetic disease characterized by painful sensitivity to light. A better understanding and...
IMPORTANCE
Erythropoietic protoporphyria (EPP) is a rare and underdiagnosed genetic disease characterized by painful sensitivity to light. A better understanding and characterization of its light-induced cutaneous symptoms may aid in the identification of EPP in patients.
OBJECTIVES
To describe the cutaneous symptoms of erythropoietic protoporphyria (EPP) and to determine if these symptoms are associated with the degree of light sensitivity.
DESIGN, SETTING, AND PARTICIPANTS
This was a cross-sectional study of adolescent and adult (≥15 years) patients with EPP across the US conducted by a single academic hospital via a remotely administered survey, measurements of light sensitivity by light dosimetry and by text message symptom assessments. Data analyses were conducted from November 2020 to April 2022.
EXPOSURES
Sunlight exposure.
MAIN OUTCOMES AND MEASURES
Self-reported symptoms and association with measured light sensitivity.
RESULTS
The study sample consisted of 35 patients with EPP (mean [SD] age, 39.1 (15.5) years; 21 [60%] female; 14 [40%] male; 35 [100%] White individuals). The patients' median [range] skin tone was 3.0 (1.0-8.0), based on self-reporting from 1 (lightest) to 12 (darkest). A total of 24 participants completed the light dosimeter measurements. Phototoxic reactions were characterized by pain (97%; 34 patients), burning (97%; 34), tingling (97%; 34), pruritus (83%; 29), allodynia (89%; 31), improvement of symptoms with cold (89%; 31), achiness (24%; 12), fatigue (46%; 16), mild swelling (83%; 29), severe swelling (63%; 22), erythema (51%; 18), petechiae (40%; 14), skin cracking (43%; 15), scabbing (46%; 16), scarring (66%; 23), and other chronic skin changes (40%; 14). Patients with EPP reported that their hands, feet, and face were most sensitive to light and that their shoulders and legs were least sensitive; 25.7% (9 patient) reported no chronic skin changes, and 5.7% (2 patients) reported never having had any visible symptoms. None of these findings varied with the degree of light sensitivity except that lower overall light sensitivity was associated with lower ranked sensitivity of the neck and arms.
CONCLUSIONS AND RELEVANCE
The findings of this cross-sectional study suggest that patients with EPP have distinctive cutaneous symptoms that may aid in identification of this underdiagnosed disease. Characteristic EPP symptoms include light-induced cutaneous burning pain and occasional swelling, particularly over the hands, with a prodrome of pruritus and paresthesias. Minimal skin changes or the absence of visible skin changes during reactions to light, including lack of erythema, do not exclude an EPP diagnosis nor suggest low EPP disease burden.
Topics: Adult; Adolescent; Humans; Male; Female; Protoporphyria, Erythropoietic; Photophobia; Cross-Sectional Studies; Erythema; Pruritus; Paresthesia
PubMed: 36630131
DOI: 10.1001/jamadermatol.2022.5850 -
Postepy Dermatologii I Alergologii Apr 2024Afamelanotide is a synthetic alpha melanocyte stimulating hormone presenting a higher activity than natural hormones. Its main properties are related to the enhanced... (Review)
Review
Afamelanotide is a synthetic alpha melanocyte stimulating hormone presenting a higher activity than natural hormones. Its main properties are related to the enhanced production of eumelanin by agonistically binding to the melanocortin-1 receptor. Since 2016 afamelanotide has been especially applied to treat cases of erythropoietic porphyria (EPP), where painful photosensitivity has been observed since early childhood. The positive effect of afamelanotide in EPP administered subcutaneously improved tolerance to artificial white light and increased pain-free time spent in direct sunlight. In this review we summarize the possible use of afamelanotide in dermatology, with special emphasis on EPP and encourage including afamelanotide as a treatment option in patient care.
PubMed: 38784937
DOI: 10.5114/ada.2024.138818 -
The Yale Journal of Biology and Medicine 1979Protoporphyria (PP) is an inherited disorder of porphyrin metabolism in man in which there is excessive accumulation and excretion of protoporphyrin. Recently, a similar... (Comparative Study)
Comparative Study Review
Protoporphyria (PP) is an inherited disorder of porphyrin metabolism in man in which there is excessive accumulation and excretion of protoporphyrin. Recently, a similar disorder has been described in cattle. In this report, the clinical, biochemical, and genetic features of bovine and human PP are compared. Human and bovine PP are characterized by photosensitivity and elevation of erythrocyte and fecal protoporphyrin levels. In both disorders, a deficiency of heme synthase activity is present in all tissues which have been examined. The diseases differ clinically in that hepatobiliary disease has been found thus far only in human PP. They also have different inheritance patterns. Human PP is an autosomal dominant disease, while initial studies strongly suggest that there is an autosomal recessive pattern of inheritance in bovine PP.
Topics: Animals; Cattle; Cattle Diseases; Cytochromes; Disease Models, Animal; Heme; Hemeproteins; Hemoglobins, Abnormal; Humans; Liver Diseases; Porphyrias; Porphyrins; Protoporphyrins
PubMed: 392959
DOI: No ID Found -
Pharmaceuticals (Basel, Switzerland) Dec 2023Erythropoietic protoporphyria (EPP) is a genetic disorder stemming from reduced ferrochelatase expression, the final enzyme in the pathway of heme biosynthesis. A... (Review)
Review
Erythropoietic protoporphyria (EPP) is a genetic disorder stemming from reduced ferrochelatase expression, the final enzyme in the pathway of heme biosynthesis. A closely related condition, X-linked protoporphyria (XLP), bears similar clinical features although it arises from the heightened activity of δ-aminolevulinic acid synthase 2 (ALAS2), the first and normally rate-controlling enzyme in heme biosynthesis in developing red blood cells. Both of these abnormalities result in the buildup of protoporphyrin IX, leading to excruciating light sensitivity and, in a minority of cases, potentially fatal liver complications. Traditionally, managing EPP and XLP involved sun avoidance. However, the emergence of innovative therapies, such as dersimelagon, is reshaping the therapeutic landscape for these conditions. In this review, we summarize salient features of the properties of dersimelagon, shedding light on its potential role in advancing our understanding of treatment options for EPP and XLP.
PubMed: 38256864
DOI: 10.3390/ph17010031 -
Genes & Genomics 2017The main purpose of present review is to describe and organize autosomal recessive disorders (arachnomelia, syndactylism, osteopetrosis, dwarfism, crooked tail syndrome,... (Review)
Review
The main purpose of present review is to describe and organize autosomal recessive disorders (arachnomelia, syndactylism, osteopetrosis, dwarfism, crooked tail syndrome, muscular hyperplasia, glycogen storage disease, protoporphyria), which occur among beef cattle, and methods that can be applied to detect these defects. Prevalence of adverse alleles in beef breeds happens due to human activity-selections of favorable features, e.g. developed muscle tissue. Unfortunately, carriers of autosomal recessive diseases are often characterized by these attributes. Fast and effective identification of individuals, that may carry faulty genes, can prevent economical losses.
PubMed: 28458779
DOI: 10.1007/s13258-017-0525-8 -
British Medical Journal Dec 1979
Topics: Erythropoiesis; Humans; Porphyrias; Protoporphyrins
PubMed: 526809
DOI: No ID Found -
Wideochirurgia I Inne Techniki... Jun 2022Erythropoietic protoporphyria is a hereditary defect in heme synthesis, causing protoporphyrin deposition and phototoxic reactions after exposure to light, especially at...
Erythropoietic protoporphyria is a hereditary defect in heme synthesis, causing protoporphyrin deposition and phototoxic reactions after exposure to light, especially at a wavelength of about 400 nm. Sensitivity to light may cause postoperative complications. Therefore, in open surgery protective filters are employed on surgical luminaires. The dangers of laparoscopy are little understood and the intensity of the light used can be high. To protect against phototoxic injury, we inserted an OG 530 filter in the video track. This filter blocks wavelengths below 470 nm. Three cholecystectomies and one sigmoidectomies were performed laparoscopically. The procedures were uneventful, and the patients suffered no adverse reactions, including phototoxic symptoms. The filter had a moderate influence on color perception and caused no significant restrictions on working conditions. We consider that it is appropriate to develop a relevant design to meet the suitable requirements for a durable filter holder in the laparoscopic video track.
PubMed: 35707342
DOI: 10.5114/wiitm.2022.115003