Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.2.1.23 (beta-galactosidase)
14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The lysosome is an intracytoplasmic acidic vacuole containing more than 60 hydrolytic enzymes for digestion of macromolecules, such as nucleic acids, proteins, lipids and complex carbohydrates. Expression of lysosomal enzyme activities is regulated by various intracellular environmental factors. Mutation of a gene coding for a lysosomal enzyme results in a specific genetic disease, often involving the central nervous system in children. Three groups of functional proteins are known at present for regulation of the expressed enzyme activity in lysosomes. Targeting of a newly synthesized protein is achieved by the mannose 6-phosphate receptor system, which was revealed in the course of I -cell disease research. Many lysosomal enzymes are excessively secreted in the extracellular compartment in the absence of this regulatory system in patients with this disease. Intralysosomal stability of beta-galactosidase is regulated by a multifunctional protein that interacts with two lysosomal enzymes, beta-galactosidase and sialidase, and also exerts catalytic activities as carboxypeptidase, esterase and deamidase under various pH conditions. It is encoded by a gene on chromosome 20, and its mutation results in a neurodegenerative disease in children and adults (galactosialidosis). For digestion of lipid substrates, lysosomal enzymes need specific activator proteins as natural detergents for molecular interaction with these nonpolar compounds. Two different groups of proteins have been revealed. A protein encoded by a gene on chromosome 5 interacts with ganglioside GM2 and its asialo derivative, for their catalytic hydrolysis by beta-hexosaminidase A. Another protein encoded by a gene on chromosome 10 is expressed as a precursor (prosaposin) which is then processed to four small proteins (saposins) with heterogeneous functions. They are essential for hydrolysis of sphingolipid substrates, and genetic deficiency of each protein results in various lipid storage diseases.
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PMID:[Lysosomal enzymes, sphingolipid activator proteins, and protective protein]. 857 30

Galactosialidosis is the inherited metabolic disease with autosomal recessive trait. This disease classifies into three classical subtypes and a variant type in clinically. In enzymatic assay, we observe the decreasing activities of both beta-galactosidase and neuraminidase, but now we know that the primarily cause of this disease is abnormality of protective protein. In 1988, the cDNA of human protective protein was cloned. From the cloning, the genetically abnormalities of this disease were detected and the difference of abnormalities about the proteins were studied between the clinical subtypes. Then, the abnormalities within the subtypes were confirmed the difference about the mature process of protective protein in expression study. The structure of this protein was shown in 1994-1995 and the abnormal mutated proteins were studied about stoichiometrical features. On the other hand, the functions of protective protein are identified to have the role of deamidase, esterase, and carboxypeptidase besides the protective function. In the galactosialidosis patients, these activities decrease in fact. We knew the reason of the difference within the subtypes of this disease using molecular biology methods at present. In the future, the model mouse will be prepared and we hope to produce the medicine for this disease.
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PMID:[Galactosialidosis--protective protein and related enzymes]. 857 44

Deficiency of lysosomal protective protein/cathepsin A in humans is the primary cause of galactosialidosis, a lysosomal storage disease characterized by combined deficiency of beta-galactosidase and neuraminidase. We have investigated 20 galactosialidosis patients and nine of their obligate heterozygous parents. A group of 12 patients with the early infantile type of the disease exhibited practically complete absence of cathepsin A activity, whereas eight patients with either the late infantile or the juvenile/adult type had 2-5% residual activity. Highest levels (5%) were present in two patients with milder clinical manifestations and later onset of the disease. In most fibroblast strains, beta-galactosidase activity was 10-15% of normal levels, whereas neuraminidase was reduced to less than 4%. Interestingly, a substantial residual activity (10%) of the latter enzyme was detected in the patient with the mildest phenotype and the highest cathepsin A activity. Heterozygous values for cathepsin A were reduced on average to half of normal levels. However, in two cell strains, the activity was far below control range, and in these cases, neuraminidase activity was severely depressed. Finally, we showed that cathepsin A had considerable activity in chorionic villi and amniocytes, but was deficient in amniocytes from a pregnancy with an affected fetus, indicating the relevance of cathepsin A assay for prenatal diagnosis of galactosialidosis.
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PMID:Cathepsin A deficiency in galactosialidosis: studies of patients and carriers in 16 families. 872 71

Few patients with the early-infantile form of galactosialidosis have been described to date. Presented here is the first Italian case. Fetal hydrops was detected by ultrasound at week 24 of gestation. At birth, the infant presented with hypotonia, massive edema, a flattened coarse facies, telangiectasias, and hepatosplenomegaly, but no dysostosis multiplex. The patient died 72 days postpartum. Excessive sialyloligosaccharides in urine, as well as vacuolation of lymphocytes and eosinophilic granulocytes in peripheral blood, were indicative of a lysosomal storage disease. In the patient's fibroblasts, both alpha-neuraminidase and beta-galactosidase activities were severely reduced, and cathepsin A activity was < 1% of control levels, confirming the biochemical diagnosis of galactosialidosis. However, in contrast to previously reported early-infantile cases, a normal amount of protective protein/cathepsin A mRNA was detected on Northern blots. This mutant transcript was translated into a precursor protein that was not processed into the mature enzyme and lacked both protective and catalytic activities.
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PMID:Early-infantile galactosialidosis: clinical, biochemical, and molecular observations in a new patient. 886 21

N-Acetylgalactosamine-6-sulfate sulfatase (GALNS) catalyzes the first step of intralysosomal keratan sulfate (KS) catabolism. In Morquio type A syndrome GALNS deficiency causes the accumulation of KS in tissues and results in generalized skeletal dysplasia in affected patients. We show that in normal cells GALNS is in a 1.27-MDa complex with three other lysosomal hydrolases: beta-galactosidase, alpha-neuraminidase, and cathepsin A (protective protein). GALNS copurifies with the complex by different chromatography techniques: affinity chromatography on both cathepsin A-binding and beta-galactosidase-binding columns, gel filtration, and chromatofocusing. Anti-human cathepsin A rabbit antiserum coprecipitates GALNS together with cathepsin A, beta-galactosidase, and alpha-neuraminidase in both a purified preparation of the 1. 27-MDa complex and crude glycoprotein fraction from human placenta extract. Gel filtration analysis of fibroblast extracts of patients deficient in either beta-galactosidase (beta-galactosidosis) or cathepsin A (galactosialidosis), which accumulate KS, demonstrates that the 1.27-MDa complex is disrupted and that GALNS is present only in free homodimeric form. The GALNS activity and cross-reacting material are reduced in the fibroblasts of patients affected with galactosialidosis, indicating that the complex with cathepsin A may protect GALNS in the lysosome. We suggest that the 1.27-MDa complex of lysosomal hydrolases is essential for KS catabolism and that the disruption of this complex may be responsible for the KS accumulation in beta-galactosidosis and galactosialidosis patients.
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PMID:Association of N-acetylgalactosamine-6-sulfate sulfatase with the multienzyme lysosomal complex of beta-galactosidase, cathepsin A, and neuraminidase. Possible implication for intralysosomal catabolism of keratan sulfate. 891 Apr 59

Human cathepsin A ("lysosomal protective protein"; E.C.3.4.16.5) is a multifunctional lysosomal protein which forms a high-molecular-weight complex with beta-galactosidase and alpha-neuraminidase, protecting them against intralysosomal proteolysis. In addition to this protective function, cathepsin A is a serine carboxypeptidase and the understanding of its catalytic function requires a definition of its substrate specificity. For this purpose, we used a combined experimental [Pshezhetsky, A. V., Vinogradova, M. V., Elsliger, M.-A., El-Zein, F., Svedas, V.K., & Potier, M. (1995) Anal. Biochem. 230, 303-307] and theoretical approach comparing cathepsin A to two different homologous carboxypeptidases of the same family: yeast carboxypeptidase Y and wheat carboxypeptidase II. We computed the energies involved in substrate binding to the S1' subsite (C-terminal) of cathepsin A using a structural model based on the X-ray structure of the homologous wheat carboxypeptidase II. The binding energies of N-blocked Phe-Xaa dipeptide substrates to the active sites of cathepsin A, wheat carboxypeptidase II, and yeast carboxypeptidase Y were estimated using a molecular mechanics force field supplemented with a solvation energy term. This theoretical analysis showed a good correlation with the experimentally determined free energies of substrate binding. This result validates the use of this approach to analyze the energetics of substrate binding to the S1' subsite and provides a rational interpretation of serine carboxypeptidase-substrate interactions in molecular terms. We conclude that the three serine carboxypeptidases have similar affinities for substrates with hydrophobic P1' amino acid residues but that the wheat enzyme has an additional capacity for binding positively charged P1' residues. Finally, the substrate specificity of human cathepsin A is very similar to that of carboxypeptidase Y, with a high binding affinity for substrates with hydrophobic P1' residues, but the affinity of cathepsin A for P1; Phe residue is higher than for the Leu residue.
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PMID:Comparative modeling of substrate binding in the S1' subsite of serine carboxypeptidases from yeast, wheat, and human. 894 54

Neuraminidases (sialidases) have an essential role in the removal of terminal sialic acid residues from sialoglycoconjugates and are distributed widely in nature. The human lysosomal enzyme occurs in complex with beta-galactosidase and protective protein/cathepsin A (PPCA), and is deficient in two genetic disorders: sialidosis, caused by a structural defect in the neuraminidase gene, and galactosialidosis, in which the loss of neuraminidase activity is secondary to a deficiency of PPCA. We identified a full-length cDNA clone in the dbEST data base, of which the predicted amino acid sequence has extensive homology to other mammalian and bacterial neuraminidases, including the F(Y)RIP domain and "Asp-boxes." In situ hybridization localized the human neuraminidase gene to chromosome band 6p21, a region known to contain the HLA locus. Transient expression of the cDNA in deficient human fibroblasts showed that the enzyme is compartmentalized in lysosomes and restored neuraminidase activity in a PPCA-dependent manner. The authenticity of the cDNA was verified by the identification of three independent mutations in the open reading frame of the mRNA from clinically distinct sialidosis patients. Coexpression of the mutant cDNAs with PPCA failed to generate neuraminidase activity, confirming the inactivating effect of the mutations. These results establish the molecular basis of sialidosis in these patients, and clearly identify the cDNA-encoded protein as lysosomal neuraminidase.
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PMID:Characterization of human lysosomal neuraminidase defines the molecular basis of the metabolic storage disorder sialidosis. 898 84

Protective protein/cathepsin A (PPCA) is a lysosomal serine carboxypeptidase that forms a complex with beta-galactosidase and neuraminidase. Its deficiency in humans leads to the lysosomal storage disorder galactosialidosis (GS). The pathologic manifestations in patients relate primarily to the severe deficiency of neuraminidase, and the physiological significance of cathepsin A activity remains unclear. The mouse model of GS, which closely resembles the human phenotype, shows that cells from numerous tissues, especially the central nervous system (CNS), are affected by this disease. To study the site and level of expression of PPCA mRNA in murine and human tissues, we analyzed the promoter regions of the corresponding genes. Their 5' genomic regions were strikingly similar in both organization and sequence. A single 1.8-kb PPCA transcript is present in humans, whereas mouse tissues have a major 1.8-kb and a minor 2.0-kb transcript, both of which are differentially expressed. These two mouse mRNA species differ only in their 5' untranslated region (UTR). The larger mRNA, unique to mouse, is transcribed from an upstream TATA-box-containing promoter, which is absent in the human gene. The downstream promoter, which transcribes the 1.8-kb mRNA common to human and mouse, has characteristics of housekeeping gene promoters and contains putative Sp1 binding sites and three USF/MLTF sequences. In vitro studies demonstrated that expression from the downstream promoter is higher than that from the upstream murine-specific promoter. In situ hybridization of mouse tissue sections identified regions of the brain that preferentially express the 2.0-kb transcript. Our results imply that PPCA mRNA distribution and regulation in murine tissues differs from that in human tissues.
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PMID:Identification of the promoters for the human and murine protective protein/cathepsin A genes. 917 65

Cathepsin A [EC 3.4.16.1], so called protective protein, occurs as an enzyme complex with lysosomal beta-galactosidase [3.2.1.23] and is involved in the stable enzymic expression of lysosomal sialidase [3.2.1.18]. In this study we investigated the enzymatic properties of cathepsin A in the bovine beta-galactosidase complex and how it is involved in the molecular multiplicities of the beta-galactosidase and sialidase complexes. Bovine protective protein homologous to the human protein had a molecular weight of 48 kDa on SDS-PAGE and cathepsin A activity optimum around pH 6.0. It hydrolyzed dipeptide substrates composed of hydrophobic amino acids much faster than any other type of substrate tested. This specificity was found to be conserved from human to a non-mammal, chicken. Immunoprecipitation using an anti beta-galactosidase antibody demonstrated that cathepsin A is a component of both the sialidase and beta-galactosidase complexes. The over 700 kDa sialidase complex depolymerized by a brief incubation at pH 7.5 and the sialidase was inactivated irreversibly via formation of an enzyme active smaller species of sialidase. The 669 kDa beta-galactosidase complex dissociated reversibly into a 120 kDa beta-galactosidase and a 170 kDa cathepsin A, but the 120 kDa beta-galactosidase, free from the cathepsin A, formed a 260 kDa aggregate under the same conditions. Inactivation of cathepsin A by heat treatment did not affect its complex forming activity. The 170 kDa protective protein dissociated into a 50 kDa one at pH 7.5, which no longer formed the complex. These findings indicate that the 170 kDa protective protein could be the minimum unit required for in vitro reconstitution of the complex, and that its complex forming activity is carried in a heat-stable domain. Both beta-galactosidase and cathepsin A activities were labile under the dissociated condition, indicating that it physiologically stabilizes not only beta-galactosidase but also itself by forming the complex.
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PMID:Protective protein in the bovine lysosomal beta-galactosidase complex. 935 58

Lysosomal sialidase occurs in a multienzyme complex that also contains beta-galactosidase and cathepsin A. We previously cloned the human lysosomal sialidase cDNA and characterized mutations in human sialidosis patients. Here, we report the cloning and expression of the mouse lysosomal sialidase cDNA and gene. The 1.77 kb cDNA encodes an open reading frame of 408 amino acids which shows high homology to the human lysosomal sialidase (80%), the rat cytosolic sialidase (65%) and viral and bacterial sialidases (50-55%). The sialidase gene is approximately 4 kb long and contains six exons. The five introns range in size from 96 to 1200 bp. Northern blot analysis revealed high expression of multiple sialidase transcripts in kidney and epididymis, moderate levels in brain and spinal cord, and low levels in adrenal, heart, liver, lung and spleen. Transient expression of the cDNA clone in sialidase-deficient SM/J mouse fibroblasts and human sialidosis fibroblasts restored normal levels of sialidase activities in both cell types. Immunocytochemically expressed sialidase co-localized with a lysosomal marker, LAMP2, confirming its lysosomal nature. Since sialidase activity requires its association with beta-galactosidase and cathepsin A, the expression of mouse sialidase within human sialidosis cells underlines the structural similarity between mouse and human enzymes and suggests that the mechanism for complex formation and function is highly conserved.
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PMID:Cloning of the cDNA and gene encoding mouse lysosomal sialidase and correction of sialidase deficiency in human sialidosis and mouse SM/J fibroblasts. 938 11


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