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)

We studied the relation of various enzymes to subpopulations of lymphocytes in man. T cell-rich fractions were separated with a nylon column from mononuclear cells in the buffy coat. Comparing the enzymatic profiles of the two fractions, we found that the difference between the two groups came from the dominancy of B cells and/or macrophages in the former fraction, and from that of T cells in the latter. The enzymes characterizing T cells included N-Ac-beta-D-glucosaminidase (GlcNAc-ase), prolyl endopeptidase (Post-Pro-Enz), and dipeptidyl aminopeptidase IV (DAP-IV), whereas those characterizing B cells and/or macrophages include poly(ADP-ribose) synthetase, leucine aminopeptidase (Leu-AP), AP-B, cathepsin B, sialidase, and AP-A. Inhibitors of these enzymes may lead to modification of the function of T and B cells.
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PMID:Multiple enzymes related to differentiation of lymphocyte subpopulations in man. 278 19

The metabolism of the cell surface glycoprotein dipeptidyl peptidase IV(DPPIV) was studied in cultured rat hepatocytes. In pulse-chase labelling experiments using L-[35S]methionine a 100-kDa high-mannose precursor polypeptide is converted into the mature complex-type 110-kDa glycoprotein. Digestion with exo- and endoglycosidases and metabolic labelling with radioactive sugars demonstrate that the 110-kDa form contains about 6 complex-type oligosaccharides which are fucosylated and sialylated. About 25 min after the beginning of the pulse-labelled glycoprotein appears in the sinusoidal membrane. Physiologically only the 110-kDa form is found in the cell surface. If cell surface DPP IV was desialylated by sialidase at 4 degrees C, it is resialylated during incubation at 37 degrees C. This oligosaccharide reprocessing indicates that the surface glycoprotein has been recycled to the cell compartment containing terminal glycosyltransferases (presumably the trans Golgi system). Two different methods demonstrate internalization of cell surface DPP IV: 1) The complex cell surface DPPIV -anti-DPP IV-antibody -L-[35S]methionine-labelled secondary goat-anti-mouse-antibody formed at 4 degrees C becomes less accessible to trypsin during incubation at 37 degrees C. 2) Part of the complex plasma membrane DPP IV-anti-DPP IV-antibody formed in the cold cannot be recognized by the radioactive secondary antibody after rewarming. Internalization is not blocked by inhibition of protein synthesis with cycloheximide. During internalization of plasma membrane DPP IV its concentration in the membrane remains constant.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Oligosaccharide reprocessing and recycling of a cell surface glycoprotein in cultured rat hepatocytes. 810 Oct 88