Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.5.1.4 (deaminase)
 5,113 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have recently diagnosed aspartylglucosaminuria (AGU) in four members of a Canadian family. AGU is a lysosomal storage disease in which asparagine-linked glycopeptides accumulate to particularly high concentrations in liver, spleen and thyroid of affected individuals. A lesser accumulation of these glycopeptides is seen in the kidney and brain, and they are also excreted in the urine. The altered metabolism in AGU results from a deficiency of the enzyme aspartylglucosaminidase (1-aspartamido-beta-N-acetylglucosamine amidohydrolase), which hydrolyses the asparagine to N-acetylglucosamine linkages of glycoproteins and glycopeptides. We have used human liver as a source of material for the purification of aspartylglucosaminidase. The enzyme has been purified to homogeneity by using heat treatment, (NH4)2SO4 fractionation, and chromatography on concanavalin A-Sepharose, DEAE-Sepharose, sulphopropyl-Sephadex, hydroxyapatite, DEAE-cellulose and Sephadex G-100. Enzyme activity was followed by measuring colorimetrically the N-acetylglucosamine released from aspartylglucosamine at 56 degrees C. The purified enzyme protein ran at a 'native' molecular mass of 56 kDa in SDS/12.5%-PAGE gels, and the enzyme activity could be quantitatively recovered at this molecular mass by using gel slices as enzyme source in the assay. After denaturation by boiling in SDS the 56 kDa protein was lost with the corresponding appearance of polypeptides alpha,beta and beta 1, lacking enzyme activity, at 24.6, 18.4 and 17.4 kDa respectively. Treatment of heat-denatured enzyme with N-glycosidase F resulted in the following decreases in molecular mass; 24.6 to 23 kDa and 18.4 and 17.4 to 15.8 kDa. These studies indicate that human liver aspartylglucosaminidase is composed of two non-identical polypeptides, each of which is glycosylated. The N-termini of alpha,beta and beta 1 were directly accessible for sequencing, and the first 21, 26 and 22 amino acids respectively were identified.
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PMID:Purification and structure of human liver aspartylglucosaminidase. 128 77

Aspartylglucosaminidase (AGA: E.C. 3.5.1.26) is a lysosomal amidase that hydrolyzes the N-acetylglucosamine-asparagine linkage as one of the final steps in the breakdown of glycoproteins. Deficiency of this enzyme results in aspartylglucosaminuria (AGU), an inherited lysosomal storage disease. In an attempt to establish the tissue-specific expression of AGA in normal individuals and in AGU patients, we adapted biochemical and immunohistochemical techniques to analyze AGA polypeptides in human cells and tissues. The biochemical analysis revealed the existence of alpha- and beta-subunit structures of AGA in all tissues. Immunohistochemical staining demonstrated a cell specificity in the distribution of AGA: immunoreactivity was strongest in hepatocytes, pyramidal cells in the cerebral cortex, and proximal tubule cells in the kidney. In tissues from AGU patients, AGA immunoreactivity could be detected in hepatocytes and in proximal tubule cells but not in the pyramidal cells. The regulation of the expression of AGA was approached by analyzing the transcript levels and the methylation of the AGA gene. Both heavy methylation of the AGA gene and the constant level of AGA mRNA were typical of a "house-hold" type of enzyme that can be found in small quantities in all tissues. This was in contrast to the variability of the amount of AGA polypeptides observed in different cells and tissues, suggesting that the expression of AGA is regulated not at the transcriptional but rather at the translational level.
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PMID:Expression of aspartylglucosaminidase in human tissues from normal individuals and aspartylglucosaminuria patients. 768 90

Deficiency of human aspartylglucosaminidase (AGA, glycosylasparaginase, EC 3.5.1.26), a lysosomal amidase, results in the lysosomal storage disease aspartylglucosaminuria (AGU). This disorder is most prevalent in the genetically isolated Finnish population. To facilitate the detailed analysis of this important enzyme, which functions in the final degradation step of glycoproteins, we developed a novel purification method which makes possible a simple five-step 5000-fold purification to apparent homogeneity of human aspartylglucosaminidase from leukocytes. This purification procedure takes advantage of the remarkable SDS resistance of aspartylglucosaminidase as SDS-sensitive proteins aggregate preferentially at low (NH4)2SO4 concentrations in the presence of SDS. This new method should be applicable to the isolation of other SDS-resistant enzymes, e.g., superoxide dismutase. The homogeneous enzyme preparation exhibited a previously unreported fully denatured 19-kDa form of the alpha-subunit of aspartylglucosaminidase on SDS-polyacrylamide gel electrophoresis as a consequence of complete coating by SDS.
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PMID:Large-scale purification of human aspartylglucosaminidase: utilization of exceptional sodium dodecyl sulfate resistance. 805 56