Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.1.53 (sialidase)
 2,694 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

AcDNA encoding a new alpha2,8-sialyltransferase (ST8Sia IV), which exhibits activity toward the alpha,2,3-linked sialic acids of N-linked oligosaccharides, was cloned from a mouse lung cDNA library by means of the PCR-based approach. The predicted amino acid sequence of ST8Sia IV showed 15.2, 56.0, and 26% identity with those of so far cloned mouse alpha2,8-sialytransferases, i.e. GD3 synthase (ST8Sia I), STX(ST8Sia II), and Sia(alpha)2,3Galbeta1,4GlcNAc(alpha)2,8-sialyl-transferase (ST8Sia III). ST8Sia IV exhibits high amino acid sequence identity (99.2%) with recently cloned hamster polysialyltransferase-1 gene, which is necessary to polysialic acid expression, but no enzymatic activity of the gene product was reported [Eckhardt, M. et al. (1995) Nature 373, 715-718]. The ST8Sia IV gene was strongly expressed in lung, heart, and spleen, but only weak expression of the gene was observed in brain, without remarkable developmental regulation. The activity of mouse ST8Sia IV was specific toward sialylated glycoproteins. The linage-specific sialidase treatment of glycoproteins as well as N-linked oligosaccharides from the glycoproteins revealed that ST8Sia IV exhibits an alpha2,8-sialytransferase activity toward alpha2,3-linked sialic acids of N-linked oligosaccharides. ST8Sia IV can synthesize polysialic acid chain in vitro without any initiator sialytransferase.
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PMID:Molecular cloning and characterization of a third type of N-glycan alpha 2,8-sialyltransferase from mouse lung. 869 Jul 32

GD3 (CD60a) and its 9-O-acetylated variant (CD60b) are intracellular regulators of apoptosis in T lymphocytes. Surface expressed 9-O-acetyl- and 7-O-acetyl-GD3 (CD60b and CD60c) may have a functional impact on activated T and B cells. In order to investigate the balance between surface and intracellular expression and synthesis and degradation of these glycosphingolipids in human lymphocytes of various differentiation stages, we analyzed (i) expression of GD3 molecules on native T and B cells and thymocytes by flow cytometry and (ii) activity and regulation of possible key enzymes for CD60a,b,c synthesis and degradation at the transcriptional level. Both, surface and cytoplasmic expression of CD60a and CD60c was highest in tonsillar T cells. In thymocytes, CD60c outweighs the other CD60 variants and was mainly found in the cytoplasm. All lymphocyte preparations contained sialate O-acetyltransferase activity producing 7-O-acetyl-GD3. Sialidase activity was highest in peripheral blood lymphocytes followed by thymocytes and tonsillar T and B cells. Transcription of GD3 synthase (ST8SiaI), the key enzyme for GD3 synthesis, was highest in tonsillar T cells, whereas transcriptional levels of sialidase NEU3 and O-acetylesterase H-Lse were lowest in activated T cells. This balance between enzymes of sialic acid metabolism may explain the strong overall staining intensity for all GD3 forms in T cells. Both CASD1, presumably encoding a sialic acid-specific O-acetyltransferase, and H-Lse showed highest transcription in peripheral B lymphocytes corresponding to the low expression of CD60b and c in these cells. Our data point to regulatory functions of these anabolic and catabolic key enzymes for the expression of GD3 and its O-acetylated variants in lymphocytes at a given differentiation stage.
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PMID:Differentially regulated expression of 9-O-acetyl GD3 (CD60b) and 7-O-acetyl-GD3 (CD60c) during differentiation and maturation of human T and B lymphocytes. 2150 5