Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.24.11 (CD10)
 9,792 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The properties of two purified peptidases derived from the intestinal brush border membrane of the rat have been investigated. The pH optima, heat stabilities, substrate specificities, and metal ion requirements of the two enzymes and the effects of inhibitors on their activities were nearly identical. The isoenzymes catalyzed the hydrolysis of a wide range of peptides containing from 2 to 8 amino acid residues. The enzymes are aminopeptidases; no evidence for carboxypeptidase or endopeptidase activity was found. For hydrolysis, there appears to be an absolute requirement for an L-amino acid at the NH2-terminus of the peptide substrate. There was a similar but less absolute requirement for the penultimate NH2-terminal amino acid. Thus, although peptides of the type L-aminoacyl-L-proline, L-aminoacyl-L-prolyl-(L-amino acid)n, or L-aminoacyl-D-amino acid were not hydrolyzed, L-leucyl-beta-naphthylamide could be utilized as a substrate. The enzymes appeared to be metalloenzymes in that metal ion-chelating agents could inhibit their activities. Co2+ partially restored the activities lost by chelation. Immunodiffusion studies showed that the two enzymes were immunologically identical. The antipeptidase antisera were specific for the enzymes and did not react with other constituents of the intestinal cell. Both enzymes have binding sites for the lectin phytohemagglutinin which recognizes N-acetylgalactosamine residues located at or near the terminal positions of glycoprotein carbohydrate chains. Both the lectin and the antibodies inhibited enzyme activities, but the mechanisms of inhibition appeared to be different.
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PMID:Rat intestinal brush border membrane peptidases. II. Enzymatic properties, immunochemistry, and interactions with lectins of two different forms of the enzyme. 0 46

mAb BW835 (IgG1) has been generated to breast cancer cell lines by alternating injections of MCF-7 or SW-613 cells and has been demonstrated to be of value in the serodiagnosis of mammary carcinoma. BW835 defines a carbohydrate epitope on integrated or secreted MUC1 glycoforms from carcinoma cells and human milk. To identify BW835-reactive glycopeptides on MUC1, proteolytic fragments of the mucin obtained by digestion with the Gly-C-specific endopeptidase IV from papaya corresponding to low molecular mass fragments (< 10 kilodaltons) of the tandem repeat domain were screened. A glycosylated fragment (glycopeptide 17) containing the mAb HMFG-2-defined epitope was highly reactive to BW835 antibody, while nonglycosylated tandem repeat peptide TAP25 or its in vitro-glycosylated N-acetylgalactosamine (GalNAc) derivatives were unreactive. Glycopeptide 17 bound to peanut agglutinin and to a Thomsen-Friedenreich antigen (TF alpha)-specific mAb (A78-G/A7). Binding of BW835 to glycopeptide 17 or to MUC1 was competitively inhibited by peanut agglutinin and by the synthetic glycopeptides TF alpha Ser or TF alpha Thr but not by their beta-anomers. Evidence for site specificity of binding by BW835 to glycopeptide 17 was revealed by demonstrating nonreactivity of the antibody to other TF alpha-expressing glycoproteins with peptide moieties lacking MUC1-specific motifs at putative glycosylation sites. The epitope of BW835 was localized to threonine within the VTSA-peptide motif by site-specific enzymatic beta-galactosylation of the synthetic tandem repeat peptide TAP25-GalNAc1 TAPPAHGVT(-O-alpha GalNAc)SAPDTRPAPGSTAPPA. This is the first report on a TF alpha-specific mAb that shows a strict peptide sequence dependency of binding.
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PMID:Monoclonal antibody BW835 defines a site-specific Thomsen-Friedenreich disaccharide linked to threonine within the VTSA motif of MUC1 tandem repeats. 754 84

We previously described a CS31A-related protein, CF29K, expressed by Klebsiella pneumoniae strains involved in nosocomial infections. In this study, we cloned and sequenced cf29A, the structural gene of the CF29K protein, and showed that CF29K is an antigenic subtype of CS31A. The CF29K protein was found to be identical to the CS31A-L protein on the basis of biochemical and immunological properties. In contrast, the CS31A-H protein presented a different apparent molecular mass during sodium dodecyl sulfate-polyacrylamide gel electrophoresis, a different limited degradation pattern with endopeptidase V8, and a specific conformational epitope. We cloned and sequenced the CS31A-L structural gene and confirmed that CF29K and CS31A-L are identical, but their major subunits differ from ClpG (the CS31A-H subtype major subunit) by one amino acid at position 89 of the mature protein, which is a lysine in CF29K instead of the asparagine in ClpG. Site-directed mutagenesis experiments demonstrated that the biochemical and immunological differences between CS31A-H and CF29K or CS31A-L were dependent only on the amino acid at position 89 of the mature protein. To study the adhesive properties of CS31A-H and CF29K in the same Escherichia coli reference strain, we performed transcomplementation experiments with the cloned CS31A major-subunit structural genes or cloned cf29A gene and the clp accessory genes of the CS31A operon. We showed that CS31A-L, CF29K, and CS31A-H were involved in adhesion to Caco-2 and Int-407 cells but not to HEp-2 cells. Nevertheless, K. pneumoniae strains and corresponding E. coli transconjugants producing CF29K adhered to cultured Caco-2, Int-407, and HEp-2 cells, indicating the expression of another R-plasmid-encoded adhesin that mediated adhesion to HEp-2 cells. The carbohydrate part of the eucaryotic receptor of CF29K and CS31A-H adhesins was investigated by adhesion inhibition experiments with Int-407 cells. Although CS31A and CF29K belong to the K88 adhesin family, the receptor does not contain N-acetyl-D-galactosamine residues but contains N-acetylneuraminic acid and N-acetyl-D-glucosamine.
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PMID:Molecular characterization and adhesive properties of CF29K, an adhesin of Klebsiella pneumoniae strains involved in nosocomial infections. 759 Oct 68

Since there is no consensus sequence directing the initial GalNAc incorporation into mucin peptides, O-glycosylation sites are not reliably predictable. We have developed a mass spectrometric sequencing strategy that allows the identification of in vivo O-glycosylation sites on mucin-derived glycopeptides. Lactation-associated MUC1 was isolated from human milk and partially deglycosylated by trifluoromethanesulfonic acid to the level of core GalNAc residues. The product was fragmented by the Arg-C-specific endopeptidase clostripain to yield tandem repeat icosapeptides starting with the PAP motif. PAP20 glycopeptides were subjected to sequencing by post-source decay matrix-assisted laser desorption ionization mass spectrometry or by solid phase Edman degradation to localize the glycosylation sites. The masses of C- or N-terminal fragments registered for the mono- to pentasubstituted PAP20 indicated that GalNAc was linked to the peptide at Ser5,Thr6 (GSTA) and Thr14 (VTSA) but contrary to previous in vitro glycosylation studies also at Thr19 and Ser15 located within the PDTR or VTSA motifs, respectively. Quantitative data from solid phase Edman sequencing revealed no preferential glycosylation of the threonines. These discrepancies between in vivo and in vitro glycosylation patterns may be explained by assuming that O-glycosylation of adjacent peptide positions is a dynamically regulated process that depends on changes of the substrate qualities induced by glycosylation at vicinal sites.
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PMID:Localization of O-glycosylation sites on glycopeptide fragments from lactation-associated MUC1. All putative sites within the tandem repeat are glycosylation targets in vivo. 931 74

We have recently shown that treatment of T cells from aged mice with an endopeptidase specific for O-linked glycoproteins can restore synapse formation and early activation markers to CD4 cells from aged mice. New data show that the sialidase from Clostridium perfringens, but not from Vibrio cholerae, can increase activation of CD4 cells from both old and young mice as measured by calcium signals, expression of CD25 and CD69, and secretion of IL-2. Lectin binding assays showed alterations with age in the levels, accessibility or conformation of multiple glycoproteins on the surface of CD4 cells. While some alterations were due to the accumulation of memory cells with age, others were age sensitive and found exclusively in the naive subset or both naive and memory subsets. Furthermore, analysis of the sialic acid links alpha(2,3)Gal/GalNAc and alpha(2,6)Gal/GalNAc in immunoprecipitated CD43 and CD45 molecules confirm that age alters the glycosylation of specific proteins that regulate TCR interaction with antigen presenting cells. These data support the idea that changes in T cell surface glycosylation could play an important role in immune senescence.
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PMID:Age-associated changes in glycosylation of CD43 and CD45 on mouse CD4 T cells. 1566 24