Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.36 (hyaluronidase)
 4,606 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Using the sialic acid-specific lectin, limulin (LPA; from Limulus polyphemus hemolymph), the distribution and nature of sialoglycoconjugates on the surface of rat pancreatic cells has been investigated. Binding of rhodaminated LPA (Rh-LPA) or horseradish peroxidase-conjugated LPA (HRP-LPA) to fixed-frozen sections of adult rat pancreas resulted in intense linear staining of the apical surface of acinar cells with fainter staining on the basal but not the lateral cell surfaces. LPA binding was specific in that it could be abolished by 1) pretreatment of tissue sections with neuraminidase or periodic acid; 2) competition with sialic acid; and 3) incubation in Ca2+ -free buffers. Pretreatment of sections with proteases abolished LPA binding to the apical surfaces of acinar cells and also enhanced LPA binding to the lateral cell surface. Lipid extraction of sections following protease treatment markedly reduced LPA binding to the acinar cell periphery. These results suggest that LPA binding sites on the acinar cell apical surface may be primarily sialoglycoproteins, while those on the basolateral surfaces may consist in part of gangliosides. Electron microscopy of collagenase-dispersed acini exposed to HRP-LPA confirmed binding of LPA to the basal plasmalemma and, in addition, revealed staining of basal lamina when present. LPA binding to the acinar cell surface was not affected by digestion of tissue sections with hyaluronidase, heparinase, collagenase, or 6 M guanidine-HCl. Control experiments indicated that rat pancreatic secretory proteins contain undetectable amounts of sialoglycoproteins and thus that the apical localization of LPA is not due to adherent secretory proteins. Islets of Langerhans were always uniformly and heavily stained with LPA conjugates; this staining was protease insensitive. Appearance of LPA binding sites was examined on embryonic pancreatic epithelia. At day 15 of gestation, Rh-LPA stained the entire periphery of the epithelial cells, including the lateral cell surface, although more intense staining was already noted on the apical surface. This pattern persisted through day 17 of gestation, but by day 19 an adult staining pattern was observed with loss of staining of the lateral cell surfaces.
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PMID:Distribution of sialoglycoconjugates on acinar cells of the mammalian pancreas. 675 68

PH-20 is a glycoprotein located on the surface of the sperm plasma membrane and on the inner acrosomal membrane. The best understood function of sperm surface PH-20 is its hyaluronidase activity, which results in hydrolysis of the hyaluronic acid-rich cumulus matrix during sperm penetration of this extracellular oocyte investment. In this study, we investigated whether alterations in the secondary and tertiary structures of sperm surface PH-20 would affect its enzyme activity. Proteins were isolated from the sperm plasma membrane by treatment of living cells with phosphatidylinositol-specific phospholipase C (PI-PLC). PH-20 was purified from the PI-PLC released proteins by immunoaffinity chromatography. Two-dimensional electrophoresis of purified PH-20 revealed 6 isoforms with isoelectric points ranging from 5.1 to 6.0. Removal of the N-linked glycans from PH-20 with N-glycosidase F shifted the molecular weight from 64 kd to approximately 54 kd, its deduced molecular weight based on sequence analysis, suggesting that most if not all, of the potential N-glycosylation sites are linked to oligosaccharides. The lectins Con A and PSA recognized purified sperm surface PH-20 after Western blotting, suggesting that mannose is a major sugar within or at the terminal end of the linked glycan. The lectins UEA and LPA did not recognize PH-20 Western blot, suggesting that fucose and sialic acid are not terminal sugars of sperm surface PH-20. Deglycosylation of sperm surface PH-20 resulted in a complete loss of its hyaluronidase activity. The reduction of disulfide bonds with beta-mercaptoethanol or dithiothreitol also resulted in loss of enzyme activity. We conclude that the hyaluronidase activity of sperm surface PH-20 is dependent on structural features established by sulfhydryl linkages, as well as glycosylation.
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PMID:Importance of glycosylation and disulfide bonds in hyaluronidase activity of macaque sperm surface PH-20. 1186 14