Disease relevance of ASPA

• In vitro expression of mutant cDNA clones demonstrated that all of these mutations led to a deficiency of ASPA and should therefore result in Canavan disease [1].
• Canavan disease is an infantile neurodegenerative disease that is due to aspartoacylase deficiency [2].
• To examine the mechanism of this enzyme the genes encoding murine and human aspartoacylase were cloned and expressed in Escherichia coli [3].
• Toxicity and expression testing was first carried out in human 293 cells, which demonstrated effective transduction of cells and high levels of functional ASPA activity [4].
• Sequence alignments show that, in particular, the regions previously suggested to form the catalytic core of human ASPA are evolutionarily conserved and nearly identical to that found in the Prochlorococcus putative ASPA [5].

High impact information on ASPA

• From the Cover: Structure of aspartoacylase, the brain enzyme impaired in Canavan disease [6].
• The structures also provide a structural framework necessary for understanding the deleterious effects of many missense mutations of human aspartoacylase [6].
• Aspartoacylase catalyzes hydrolysis of N-acetyl-l-aspartate to aspartate and acetate in the vertebrate brain [6].
• The catalytic site of aspartoacylase shows close structural similarity to those of carboxypeptidases despite only 10-13% sequence identity between these proteins [6].
• ASPA acts to hydrolyze N-acetylaspartate (NAA) into l-aspartate and acetate, but the connection between ASPA deficiency and the failure of proper CNS development is unclear [7].

Chemical compound and disease context of ASPA

• Our success in preparing the recombinant ASPA in high purity should permit multiple lines of investigations to understand the pathogenic mechanisms of Canavan disease and the functional roles of NAA [8].

Biological context of ASPA

• Mutations in ASPA that lead to loss of enzymatic activity have been identified, and E285A and Y231X are the two predominant mutations that account for 97% of the mutant chromosomes in Ashkenazi Jewish patients [1].
• Both patients were found to be compound heterozygotes for C914A (A305E) and G212A (R71H) mutations in ASPA [9].
• Since both TAC and TAT code for tyrosine, this sequence polymorphism has no effect on the amino acid sequence of the ASPA protein [10].
• More interestingly, the product of N-acetylasparagine was aspartate but not asparagine, indicating that ASPA catalyzed deacetylation as well as hydrolysis of the beta acid amide [8].
• Two novel aspartoacylase gene (ASPA) missense mutations specific to Norwegian and Swedish patients with Canavan disease [11].

Anatomical context of ASPA

• The results of transient expression of the mutant ASPA cDNA containing these mutations in COS-7 cells and assays for ASPA activity of patient fibroblasts indicated that these mutations were responsible for the enzyme deficiency [12].
• Fibroblasts from the patient are deficient in aspartoacylase activity [13].
• As a result of aspartoacylase deficiency, NAA builds up in extracellular fluids (ECF) and is excreted in urine [14].
• We evaluated the functional effects of rAAV-hASPA-GFP-mediated ASPA expression by standard histological methods, magnetic resonance spectroscopy (MRS) for in vivo NAA levels, and magnetic resonance imaging of CD mice. rAAV-hASPA-injected animals displayed a remarkable lack of spongiform degeneration in the thalamus [15].
• After it was confirmed that AxASPA-infected HeLa cells expressed ASPA in vitro, AxASPA or AxLacZ was administered into the left lateral ventricle of 11-week-old SER [16].

Associations of ASPA with chemical compounds

• Aspartoacylase catalyzes the deacetylation of N-acetylaspartic acid (NAA) in the brain to produce acetate and L-aspartate [3].
• A description is give of the effect on the ASPA cement reaction of tartaric acid incorporated in the cement liquid [17].
• 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 [18].
• The retentive capacity of the Whaledent Parapost system utilizing ASPA cement was compared at two lengths, three diameters, and with respect to the effect of both medication and citric acid pretreatment [19].
• The release of fluoride from a glass ionomer cement (ASPA) was compared with that from a silicate cement [20].

Other interactions of ASPA

• They differ also from other N-acylamino acid amidohydrolases: aminoacylase (EC 3.5.1.14) and aspartoacylase (EC 3.5.1.15) [21].
• None of the monkeys demonstrated significant adverse effects, and at 1 month the 2 LPD/pAAVaspa monkeys were positive for human ASPA transcript by reverse transcriptase polymerase chain reaction of brain tissue punches [4].

Analytical, diagnostic and therapeutic context of ASPA

• Future studies of ASPA enzyme structure and gene regulation in these subjects could lead to a better understanding of Canavan's pathophysiology and improvements in ASPA gene therapy [9].
• Three to five months after the injection, we determined the presence of ASPA in the CD mouse brain by ASPA activity assay, GFP expression, and Western blot analysis [15].
• We have developed a PCR assay named ASPA (allele-specific primer amplification) to determine the HPA-5a and -5b genotypes [22].
• Immunohistochemistry showed cytoplasmic and nuclear ASPA staining, the specificity of which was demonstrated by its absence from tissues of the Tremor rat, an ASPA-null mutant [23].
• Whereas two recent reports have indicated that ASPA exists as a dimer, size-exclusion chromatography of subcellular fractions showed ASPA is an active monomer in both subcellular fractions [23].

References