Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.4.4 (adenosine deaminase)
 5,136 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In 15%-20% of children with severe combined immunodeficiency (SCID), the underlying defect is adenosine deaminase (ADA) deficiency. The overall goal of our research has been to identify the precise molecular defects in patients with ADA-deficient SCID. In this study, we focused on a patient whom we found to have normal sized ADA mRNA by Northern analysis and an intact ADA structural gene by Southern analysis. By cloning and sequencing this patient's ADA cDNA, we found a C-to-T point mutation in exon 11. This resulted in the amino acid substitution of a valine for an alanine at position 329 of the ADA protein. Sequence analysis revealed that this mutation created a new BalI restriction site. Using Southern analyses, we were able to directly screen individuals to determine the frequency of this mutation. By combining data on eight families followed at our institution with data on five other families reported in the literature, we established that five of 13 patients (seven of 22 alleles) with known or suspected point mutations have this defect. This mutation was found to be associated with three different ADA haplotypes. This argues against a founder effect and suggests that the mutation is very old. In summary, a conservative amino acid substitution is found in a high proportion of patients with ADA deficiency; this can easily be detected by Southern analysis.
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PMID:A high proportion of ADA point mutations associated with a specific alanine-to-valine substitution. 277 32

Adenosine deaminase (ADA; adenosine aminohydrolase, EC 3.5.4.4) deficiency is one cause of the genetic disease severe combined immunodeficiency. To identify mutations responsible for ADA deficiency, we synthesized cDNAs to ADA mRNAs from two cell lines, GM2756 and GM2825A, derived from ADA-deficient immunodeficient patients. Sequence analysis of GM2756 cDNA clones revealed a different point mutation in each allele that causes amino acid changes of alanine to valine and arginine to histidine. One allele of GM2825A also has a point mutation that causes an alanine to valine substitution. The other allele of GM2825A was found to produce an mRNA in which exon 4 had been spliced out but had no other detrimental mutations. S1 nuclease mapping of GM2825A mRNAs showed equal abundance of the full-length ADA mRNA and the ADA mRNA that was missing exon 4. Several of the ADA cDNA clones extended 5' of the major initiation start site, indicating multiple start sites for ADA transcription. The point mutations in GM2756 and GM2825A and the absence of exon 4 in GM2825A appear to be directly responsible for the ADA deficiency. Comparison of a number of normal and mutant ADA cDNA sequences showed a number of changes in the third base of codons. These changes do not affect the amino acid sequence. Analyses of ADA cDNAs from different cell lines detected aberrant RNA species that either included intron 7 or excluded exon 7. Their presence is a result of aberrant splicing of pre-mRNAs and is not related to mutations that cause ADA deficiency.
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PMID:Mutations in the human adenosine deaminase gene that affect protein structure and RNA splicing. 347 10

Human adenosine deaminase (ADA) is an important purine catabolic enzyme which irreversibly deaminates adenosine and deoxyadenosine. Severe genetic deficiency of ADA leads to an immunological deficiency state in which T-lymphoid cells are selectively destroyed by the accumulation of toxic levels of deoxyadenosine and deoxy-ATP. In preparation for transfer of ADA sequences into a variety of cell types, we explored expression of ADA cDNAs transfected into cultured cells within a simian virus 40-based expression vector. After transfection into monkey kidney (COS) cells, ADA cDNA encompassing the entire coding region of the protein generated human ADA activity. An unexpected finding, however, was the identification of a cDNA clone that failed to produce either human enzyme activity or immunoreactive ADA protein. As this pattern is typical of many naturally occurring mutant ADA alleles, we characterized the molecular defect in this clone. DNA sequence analysis revealed a single nucleotide substitution in amino acid position 50 (glycine-valine). Northern blotting with a unique 17-mer oligonucleotide demonstrated the absence of the mutant sequence in the mRNA from which the cDNA library giving rise to the mutant cDNA was constructed. Therefore, the substitution in the variant cDNA was created during cloning. These data define one critical region of the human ADA protein molecule and suggest a convenient strategy for characterization of the phenotypes associated with naturally occurring mutant alleles.
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PMID:Transient expression of human adenosine deaminase cDNAs: identification of a nonfunctional clone resulting from a single amino acid substitution. 383 97

Autophagy, measured in isolated rat hepatocytes as the sequestration of electroinjected [3H]raffinose, was moderately (17%) inhibited by adenosine (0.4 mM) alone, but more strongly (85%) in the presence of the adenosine deaminase inhibitor, 2'-deoxycoformycin (50 microM), suggesting that metabolic deamination of adenosine limited its inhibitory effectiveness. The adenosine analogs, 6-methylmercaptopurine riboside and N6,N6-dimethyladenosine, inhibited autophagy by 89% and 99%, respectively, at 0.5 mM, probably reflecting the adenosine deaminase-resistance of their 6-substitutions. 5-Iodotubercidin (10 microM), an adenosine kinase inhibitor, blocked the conversion of adenosine to AMP and largely abolished the inhibitory effects of both adenosine and its analogs, indicating that AMP/nucleotide formation was required for inhibition of autophagy. Inhibition by adenosine of autophagic protein degradation, measured as the release of [14C]valine from prelabelled protein, was similarly potentiated by deoxycoformycin and prevented by iodotubercidin. Inhibition of autophagy by added AMP, ADP or ATP (0.3-1 mM) was, likewise, potentiated by deoxycoformycin and prevented by iodotubercidin, suggesting dephosphorylation to adenosine and intracellular re-phosphorylation to AMP. Suppression of autophagy by AMP may be regarded as a feedback inhibition of autophagic RNA degradation, or as an aspect of the general down-regulation of energy-requiring processes that occurs under conditions of ATP depletion, when AMP levels are high.
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PMID:Inhibition of hepatocytic autophagy by adenosine, adenosine analogs and AMP. 986 7

The deamination of adenosine to inosine at the wobble position of tRNA is an essential post-transcriptional RNA modification required for wobble decoding in bacteria and eukaryotes. In humans, the wobble inosine modification is catalyzed by the heterodimeric ADAT2/3 complex. Here, we describe novel pathogenic ADAT3 variants impairing adenosine deaminase activity through a distinct mechanism that can be corrected through expression of the heterodimeric ADAT2 subunit. The variants were identified in a family in which all three siblings exhibit intellectual disability linked to biallelic variants in the ADAT3 locus. The biallelic ADAT3 variants result in a missense variant converting alanine to valine at a conserved residue or the introduction of a premature stop codon in the deaminase domain. Fibroblast cells derived from two ID-affected individuals exhibit a reduction in tRNA wobble inosine levels and severely diminished adenosine tRNA deaminase activity. Notably, the ADAT3 variants exhibit impaired interaction with the ADAT2 subunit and alterations in ADAT2-dependent nuclear localization. Based upon these findings, we find that tRNA adenosine deaminase activity and wobble inosine modification can be rescued in patient cells by overexpression of the ADAT2 catalytic subunit. These results uncover a key role for the inactive ADAT3 deaminase domain in proper assembly with ADAT2 and demonstrate that ADAT2/3 nuclear import is required for maintaining proper levels of the wobble inosine modification in tRNA.
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PMID:Identification and rescue of a tRNA wobble inosine deficiency causing intellectual disability disorder. 3276 16