Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

N-Acetylaspartate (NAA) is an abundant amino acid derivative of the central nervous system that is localized primarily in neurons and has found widespread use in clinical NMR spectroscopy (MRS) as a non-invasive indicator of neuronal survival and/or viability. Its function, although still obscure, is thought to reflect its unusual metabolic compartmentalization wherein NAA synthase occurs in the neuron and aspartoacylase, the hydrolytic enzyme that removes the acetyl moiety, occurs in myelin and glia. The NAA synthase enzyme, acetyl-CoA/l-aspartate N-acetyltransferase (ANAT), was previously shown to function in mitochondria (MIT), although other subcellular fractions were apparently not examined. In this study we confirmed its presence in MIT but also found significant activity in rat brain microsomes (MIC). The reaction mixture, consisting of [(14)C]aspartate plus acetyl-CoA in Na-phosphate buffer (pH 7), gave rise to [(14)C]NAA that was separated and quantified by TLC. Reaction rates were 29.0+/-0.46 and 6.27+/-0.27 nmol/h/mg for MIC and MIT, respectively. K(m) values and pH optima were similar, and both fractions showed modest enhancement of ANAT activity with the detergents Triton CF-54 and CHAPS. Our tentative conclusion is that ANAT is bimodally targeted to MIT and a component of MIC-likely endoplasmic reticulum. ANAT activity increased in both MIC and MIT between 29 and 60 days of age but differed thereafter in that only MIT ANAT showed a decrease after 1 year.
Brain Res Mol Brain Res 2004 Mar 17
PMID:N-Acetylaspartate synthase is bimodally expressed in microsomes and mitochondria of brain. 1499 17

Canavan disease is an early onset leukodystrophy associated with psychomotor retardation, seizures, and premature death. This disorder is caused by mutations in the gene encoding the enzyme aspartoacylase (ASPA). Normally, ASPA is enriched in oligodendrocytes and ASPA deficiency results in elevated levels of its substrate molecule, N-acetylaspartate (NAA), brain edema, and dysmyelination. Using adeno-associated virus, we permanently expressed ASPA in CNS neurons of the tremor rat, a genetic model of Canavan disease, and examined the efficacy of the treatment by monitoring NAA metabolism, myelination, motor behavior, and seizures. Assessment of ASPA protein and enzyme activity in whole brain hemispheres showed restoration to normal levels as long as 6 months after treatment. This finding correlated with a reduction of NAA levels, along with a rescue of the seizure phenotype. However, gross brain pathology, such as dilated ventricles and spongiform vacuolization, was unchanged. Moreover, hypomyelination and motor deficits were not resolved by ASPA gene transfer. Our data suggest that NAA-mediated neuronal hyperexcitation but not oligodendrocyte dysfunction can be compensated for by neuronal ASPA expression.
Mol Ther 2005 May
PMID:Restoration of aspartoacylase activity in CNS neurons does not ameliorate motor deficits and demyelination in a model of Canavan disease. 1585 Oct 13

The tremor rat is a spontaneous epilepsy model with a seizure phenotype caused by a deletion in the aspartoacylase (ASPA) gene. The absence of ASPA expression in these animals results in undetectable levels of enzyme activity and the accumulation of the substrate N-acetyl-aspartate (NAA) in brain, leading to generalized myelin vacuolation and severe motor and cognitive impairment. In support of human gene therapy for CD, recombinant adeno-associated viral vector (AAV-2) expressing ASPA was stereotactically delivered to the tremor rat brain and effects on the mutant phenotype were measured. AAV-ASPA gene transfer resulted in elevated aspartoacylase bioactivity compared to untreated mutant animals and elicited a significant decrease in the pathologically elevated whole-brain NAA levels. Assessment of motor function via quantitative rotorod testing demonstrated that rats injected with AAV-ASPA significantly improved on tests of balance and coordinated locomotion compared to animals receiving control vectors. This study provides evidence that AAV-2-mediated aspartoacylase gene transfer to the brain improves biochemical and behavioral deficits in tremor rat mutants (tm/tm) and supports the rationale of human gene transfer for Canavan disease.
Brain Res Mol Brain Res 2005 Apr 27
PMID:Effects of AAV-2-mediated aspartoacylase gene transfer in the tremor rat model of Canavan disease. 1585 74

Canavan disease (CD) is an autosomal-recessive neurodegenerative disorder caused by inactivation of the enzyme aspartoacylase (ASPA, EC 3.5.1.15) due to mutations. ASPA releases acetate by deacetylation of N-acetylaspartate (NAA), a highly abundant amino acid derivative in the central nervous system. CD results in spongiform degeneration of the brain and severe psychomotor retardation, and the affected children usually die by the age of 10. The pathogenesis of CD remains a matter of inquiry. Our hypothesis is that ASPA actively participates in myelin synthesis by providing NAA-derived acetate for acetyl CoA synthesis, which in turn is used for synthesis of the lipid portion of myelin. Consequently, CD results from defective myelin synthesis due to a deficiency in the supply of the NAA-derived acetate. The demonstration of the selective localization of ASPA in oligodendrocytes in the central nervous system (CNS) is consistent with the acetate deficiency hypothesis of CD. We have tested this hypothesis by determining acetate levels and studying myelin lipid synthesis in the ASPA gene knockout model of CD, and the results provided the first direct evidence in support of this hypothesis. Acetate supplementation therapy is proposed as a simple and inexpensive therapeutic approach to this fatal disease, and progress in our preclinical efforts toward this goal is presented.
Mol Cell Endocrinol 2006 Jun 27
PMID:Canavan disease and the role of N-acetylaspartate in myelin synthesis. 1664 92

Breakdown of oligodendrocyte-neuron interactions in white matter (WM), such as the loss of myelin, results in axonal dysfunction and hence a disruption of information processing between brain regions. The major feature of leukodystrophies is the lack of proper myelin formation during early development or the onset of myelin loss late in life. These early childhood WM diseases are described as hypomyelination or dysmyelination arising from a primary block in normal myelin synthesis because of a genetic mutation expressed in oligodendrocytes, or failure in myelination secondary to neuronal or astroglial dysfunctions (van der Knaap 2001 Dev. Med. Child Neurol. 43:705-712). Here, we describe the pathophysiological parameters of Canavan disease (CD), caused by genetic mutations of the aspartoacylase (ASPA) gene, a metabolic enzyme restricted in the central nervous system (CNS) to oligodendrocytes. CD presents pathophysiological dysfunctions similar to diseases caused by myelin gene mutations, such as Pelizaeus-Merzbacher disease (PMD) and several animal models, such as myelin deficient rat (md), jimpy (jp), shiverer (sh), and quaking (qk viable) mutant mice. These single gene mutations have pleiotropic effects, whereby the alteration of one myelin gene expression disrupts functional expression of other oligodendrocyte genes with an outcome of hypomyelination/dysmyelination. Among all of the known leukodystrophies, CD is the first disorder, which was approved and tested for the adeno-associated virus vector (AAV)-ASPA gene therapy (Leone et al. 2000 Ann. Neurol. 48:27-38; Janson et al. 2001 Trends Neurosci. 24:706-712) without much success following the first two attempts. ASPA gene delivery attempts in animal models have shown a lowering of N-acetyl L-aspartate and a change in motor functions, while sponginess of the WM, a characteristic of CD remained unchanged (Matalon et al. 2003 Mol. Ther. 7 (5, Part 1):580-587; McPhee et al. 2005 Brain Res. Mol. Brain Res. 135:112-121) even with better viral serotype and delivery of the gene during early phase of development (Klugmann et al. 2005 Mol. Ther. 11:745-753). While different approaches are being sought for the success of gene therapy, there are pivotal developmental questions to address regarding the specific regions of the CNS and cell lineages that become the target for the onset and progression of CD symptoms from early to late stages of development.
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PMID:Canavan disease: a white matter disorder. 1680 7

Canavan disease (CD), an autosomal recessive neurodegenerative disorder, is caused by mutations in the aspartoacylase (ASPA) gene. In the present study, the ASPA gene was analyzed in 24 non-Jewish patients with CD from 23 unrelated families. Within this cohort, we found three large novel deletions of approximate 92, 56, and 12.13 kb in length, using both self-ligation of restriction endonuclease-digested DNA fragments with long-distance inverse PCR and multiplex dosage quantitative PCR analysis of genomic DNA. The 92 kb large deletion results in complete absence of the ASPA gene in one homozygous and one compound heterozygous patient, respectively. The 56 kb large deletion causes absence of the majority of the ASPA gene except for exon 1 alone in a compound heterozygous patient. The 12.13 kb deletion involves deletion of the ASPA gene from intron 3 to intron 5 including exons 4 and 5 (I3 to E4E5I5) in a compound heterozygous patient. Patients with the three large deletions clinically manifested severe symptoms at birth, including seizures. Our study showed that the combined use of long-distance inverse PCR and multiplex dosage quantitative PCR analysis of genomic DNA is a helpful and rapid technique to search for large deletions, particularly for detection of large deletions in compound heterozygous patients.
Mol Genet Metab
PMID:Rapid detection of three large novel deletions of the aspartoacylase gene in non-Jewish patients with Canavan disease. 1685 7

N-acetylaspartic acid (NAA) is converted into aspartate and acetate by aspartoacylase. Abnormal levels of the enzyme leads to accumulation of NAA and these changes have been observed in Canavan disease and type 2 diabetes. How upregulation of NAA affect the gastrointestine protein levels and the function is not known. Incubation of rat stomach tissue with NAA 1.5 mM, 1.5 microM and 1.5 nM induced inflammatory agents TNFalpha, p38MAPK, iNOS, PKC, COX2 and ICAM3; transcription factors phospho-NF-kBp65, cjun and cfos; contractile proteins MLCK and phospho MLC; and calcium channel alpha1C and calcium channel, voltage-dependent, beta 3 subunit compared to their respective control. Incubation of circular smooth muscle cells with the above doses of NAA induced contractility compared to the control. These studies suggest that NAA alters proteins levels and smooth muscle contractility and these changes likely to contribute to gastrointestinal disorder seen in these diseases.
Mol Biol Rep 2009 Jan
PMID:Upregulation of N-acetylaspartic acid alters inflammation, transcription and contractile associated protein levels in the stomach and smooth muscle contractility. 1794 58

The active-site dynamics of human brain aspartoacylase (hASPA) complexed with its substrate (N-acetyl-L-aspartate) has been studied using a hybrid quantum mechanical/molecular mechanical (QM/MM) approach based on the self-consistent charge-density functional tight-binding (SCC-DFTB) model. The Michaelis complex, which is constructed from a recent X-ray structure of the human brain aspartoacylase with a stable tetrahedral intermediate analogue, is reproduced in 1ns molecular dynamics simulations at 300K. The simulation shows that the substrate is tightly held in the active site by a hydrogen bond network and the putative nucleophilic water molecule is reasonably close to the nucleophilic center. The catalysis is further modeled with the density functional theory (DFT) in a truncated active-site model at the B3LYP/6-31G(d) level of theory. The DFT calculations indicate the reaction proceeds via a water promoted pathway with Glu178 serving as the general base and general acid. Transition state stabilization for nucleophilic addition is achieved by formations of the weak coordination bond between the substrate carbonyl oxygen atom and the zinc ion as well as of the strong hydrogen bonds between the substrate carbonyl oxygen atom and Arg63.
J Mol Graph Model 2010 Jun
PMID:Molecular dynamics and density functional theory studies of substrate binding and catalysis of human brain aspartoacylase. 2022 13

Canavan disease is a fatal neurological disease without any effective treatments to slow the relentless progress of this disorder. Enzyme replacement therapy has been used effectively to treat a number of metabolic disorders, but the presence of the blood-brain-barrier presents an additional challenge in the treatment of neurological disorders. Studies have begun with the aim of establishing a treatment protocol that can effectively replace the defective enzyme in Canavan disease patients. The human enzyme, aspartoacylase, has been cloned, expressed and purified, and the surface lysyl groups modified through PEGylation. Fully active modified enzymes were administered to mice that are defective in this enzyme and that show many of the symptoms of Canavan disease. Statistically significant increases in brain enzyme activity levels have been achieved in this animal model, as well as decreases in the elevated substrate levels that mimic those found in Canavan disease patients. These results demonstrate that the modified enzyme is gaining access to the brain and functions to correct this metabolic defect. The stage is now set for a long term study to optimize this enzyme replacement approach for the development of a treatment protocol.
Mol Genet Metab 2011 Feb
PMID:Modification of aspartoacylase for potential use in enzyme replacement therapy for the treatment of Canavan disease. 2109 51

Canavan disease (CD MIM#271900) is a rare autosomal recessive neurodegenerative disorder presenting in early infancy. The course of the disease is variable, but it is always fatal. CD is caused by mutations in the ASPA gene, which codes for the enzyme aspartoacylase (ASPA), which breaks down N-acetylaspartate (NAA) to acetate and aspartic acid. The lack of NAA-degrading enzyme activity leads to excess accumulation of NAA in the brain and deficiency of acetate, which is necessary for myelin lipid synthesis. Glyceryltriacetate (GTA) is a short-chain triglyceride with three acetate moieties on a glycerol backbone and has proven an effective acetate precursor. Intragastric administration of GTA to tremor mice results in greatly increased brain acetate levels, and improved motor functions. GTA given to infants with CD at a low dose (up to 0.25 g/kg/d) resulted in no improvement in their clinical status, but also no detectable toxicity. We present for the first time the safety profile of high dose GTA (4.5 g/kg/d) in 2 patients with CD. We treated 2 infants with CD at ages 8 months and 1 year with high dose GTA, for 4.5 and 6 months respectively. No significant side effects and no toxicity were observed. Although the treatment resulted in no motor improvement, it was well tolerated. The lack of clinical improvement might be explained mainly by the late onset of treatment, when significant brain damage was already present. Further larger studies of CD patients below age 3 months are required in order to test the long-term efficacy of this drug.
Mol Genet Metab 2011 Jul
PMID:A safety trial of high dose glyceryl triacetate for Canavan disease. 2147 53


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