Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026838 (spasticity)
 6,471 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A male infant with ornithine transcarbamylase (OTC) deficiency is described who was relatively symptom free for 4 months, gradually developed severe spasticity due to cerebral atrophy, and died at 13 months of age. Liver OTC activity was 1.5% of the normal mean. The mutant OTC showed an increased apparent Km for ornithine and an increased pH optimum. These kinetic findings fail to explain the atypical clinical course. The clinical picture of patients with genetic OTC deficiency who present during acute exacerbations together with the elevation of serum glutamic oxaloacetic transaminase and microvesicular fat accumulation in liver, as seen in this case, may suggest Reye's syndrome; however, electronmicroscopic examination of this patient suggested that the normal appearance of mitochondria helps to distinguish the two.
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PMID:Atypical clinical course of ornithine transcarbamylase deficiency due to a new mutant (comparison with Reye's disease). 42 91

As a toxic metabolic byproduct in mammals, excess ammonia is converted into urea by a series of five enzymatic reactions in the liver that constitute the urea cycle. A portion of this cycle takes place in the mitochondria, while the remainder is cytosolic. Liver arginase (L-arginine ureahydrolase, A1) is the fifth enzyme of the cycle, catalyzing the hydrolysis of arginine to ornithine and urea within the cytosol. Patients deficient in this enzyme exhibit hyperargininemia with episodic hyperammonemia and long-term effects of mental retardation and spasticity. However, the hyperammonemic effects are not so catastrophic in arginase deficiency as compared to other urea cycle defects. Earlier studies have suggested that this is due to the mitigating effect of a second isozyme of arginase (AII) expressed predominantly in the kidney and localized within the mitochondria. In order to explore the curious dual evolution of these two isozymes, and the ways in which the intriguing, aspects of AII physiology might be exploited for gene replacement therapy of AI deficiency, the cloned cDNA for human AI was inserted into an expression vector downstream from the mitochondrial targeting leader sequence for the mitochondrial enzyme ornithine transcarbamylase and transfected into a variety of recipient cell types. AI expression in the target cells was confirmed by northern blot analysis, and competition and immunoprecipitation studies showed successful translocation of the exogenous AI enzyme into the transfected cell mitochondria. Stability studies demonstrated that the translocated enzyme had a longer half-life than either native cytosolic AI or mitochondrial AII. Incubation of the transfected cells with increasing amounts of arginine produced enhanced levels of mitochondrial AI activity, a substrate-induced effect that we have previously seen with native AII but never AI. Along with exploring the basic biological questions of regulation and subcellular localization in this unique dual-enzyme system, these results suggest that the mitochondrial matrix space may be a preferred site for delivery of enzymes in gene replacement therapy.
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PMID:Delivery of cytosolic liver arginase into the mitochondrial matrix space: a possible novel site for gene replacement therapy. 913 Oct 18

Two forms of arginase, both catalyzing the hydrolysis of arginine to ornithine and urea, are found in animals ranging from amphibians to mammals. In humans, inherited deficiency of hepatic or type I arginase results in hyperargininemia, a syndrome characterized by periodic episodes of hyperammonemia, spasticity, and neurological deterioration. In these patients, a second extrahepatic or type II arginase activity is significantly increased, an induction that may partially compensate for the lack of AI activity and apparently mitigates some of the clinical effects of the condition. Cloning and characterization of the human AII cDNA was recently accomplished. The cloning, sequencing, and partial characterization of the mouse and rat AII cDNAs are reported herein. The DNA sequences predicted polypeptides of 354 amino acids, including a N-terminal mitochondrial import signal. Sequence homology to the human type II arginase, arginase activity data, and immunoprecipitation with an anti-AII antibody confirm the identity of these cloned genes as rodent extrahepatic type II arginases.
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PMID:Cloning and characterization of the mouse and rat type II arginase genes. 960 38

Deficiency of liver arginase (AI) causes hyperargininemia (OMIM 207800), a disorder characterized by progressive mental impairment, growth retardation, and spasticity and punctuated by sometimes fatal episodes of hyperammonemia. We constructed a knockout mouse strain carrying a nonfunctional AI gene by homologous recombination. Arginase AI knockout mice completely lacked liver arginase (AI) activity, exhibited severe symptoms of hyperammonemia, and died between postnatal days 10 and 14. During hyperammonemic crisis, plasma ammonia levels of these mice increased >10-fold compared to those for normal animals. Livers of AI-deficient animals showed hepatocyte abnormalities, including cell swelling and inclusions. Plasma amino acid analysis showed the mean arginine level in knockouts to be approximately fourfold greater than that for the wild type and threefold greater than that for heterozygotes; the mean proline level was approximately one-third and the ornithine level was one-half of the proline and ornithine levels, respectively, for wild-type or heterozygote mice--understandable biochemical consequences of arginase deficiency. Glutamic acid, citrulline, and histidine levels were about 1.5-fold higher than those seen in the phenotypically normal animals. Concentrations of the branched-chain amino acids valine, isoleucine, and leucine were 0.4 to 0.5 times the concentrations seen in phenotypically normal animals. In summary, the AI-deficient mouse duplicates several pathobiological aspects of the human condition and should prove to be a useful model for further study of the disease mechanism(s) and to explore treatment options, such as pharmaceutical administration of sodium phenylbutyrate and/or ornithine and development of gene therapy protocols.
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PMID:Mouse model for human arginase deficiency. 1205 59

The Hyperornithinemia-Hyperammonemia-Homocitrullinuria (HHH) syndrome is a disorder of the urea cycle and ornithine degradation pathway caused by mutations in the mitochondrial ornithine transporter, ORNT1 (SLC25A15). In general, the majority of patients with HHH syndrome come to medical attention during infancy or early school years with symptoms such as learning disabilities, changes in cognitive development, spasticity, or liver dysfunction. In this report, we describe a 35-year-old male of Indian descent who was diagnosed with HHH syndrome after he presented to the emergency room with gastroenteritis, disorientation, and slurred speech. Molecular analysis revealed that this patient was heterozygous for two ORNT1 mutations, p.[Gly220Arg(+)Arg275X] (c.[658G>A(+)823C>T]) that had been previously reported in homozygous probands who presented during the first year of life. Cellular studies revealed that the ORNT1 p.Gly220Arg mutation was nonfunctional but targeted to the mitochondria. Given that this patient was a successful college graduate on a vegetarian diet without a prior history of learning or neurological impairment, additional factors such as gene redundancy, environmental, and epigenetic factors may have contributed to the delay in onset of presentation and lack of any previous symptoms. To the best of our knowledge, this is the first reported case of an adult-onset HHH syndrome presentation without a prior history of neurological or cognitive deficiency.
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PMID:Adult-onset presentation of a hyperornithinemia-hyperammonemia-homocitrullinuria patient without prior history of neurological complications. 2343 Aug 80