Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0393754 (HSA)
 2,996 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The enzyme that catalyzed the conversion of human salivary alpha-amylase family A (HSA-A) to family B (HSA-B) was identified. It was partially purified from the precipitate obtained by centrifugation of human saliva at 105,000 x g for 60 min by solubilization with 3[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate and column chromatographies with Sephacryl S-300-HR and hydroxylapatite. The enzyme preparation was practically free from contaminating exoglycosidases and proteases. The enzyme cleaved the N,N'-diacetylchitobiose moiety of the sugar chain of HSA-A, as shown by the isolation of the protein moiety which contained 1 GlcNAc and 1 Fuc residue and the sugar chain (Gal)2(Fuc)1(GlcNAc)2(Man)3(GlcNAc). This enzyme also cleaved the N,N'-diacetylchitobiose moiety of the sugar chain of human transferrin tetraglycopeptide Asn-Tyr-Asn(GlcNAc)2(Man)3(GlcNAc)2(Gal)2-Lys to yield equimolar amounts of peptide Asn-Tyr-Asn(GlcNAc)Lys and sugar chain (Gal)2(GlcNAc)2(Man)3(GlcNAc). The enzyme was identified as an endo-beta-N-acetylglucosaminidase. The enzyme acted on HSA-A with desialylated and defucosylated outer chain moieties of the sugar chains at a similar rate as that of native HSA-A. The enzyme activity was reduced to 13 and 5% using HSA-A with the sugar chains whose outer chain moieties lacked Gal and GlcNAc, respectively, from the nonreducing end. The enzyme also acted on human transferrin, calf fetuin, and asparagine oligosaccharides of transferrin and fetuin. On the other hand, the enzyme did not act on ovalbumin, RNase B, Taka-amylase, yeast invertase, and ovalbumin asparagine oligosaccharides. These results indicate that human salivary endo-beta-N-acetylglucosaminidase is specific for complex type sugar chains and can release the sugar chains from native glycoproteins and glycopeptides regardless of the existence of a Fuc residue on the proximal GlcNAc of the N,N'-diacetylchitobiose core of their sugar chains. The source of the enzyme was epithelial cells peeling from the oral cavity epithelium into saliva. The enzyme was thought to be integrated on the surface of the epithelial cell membrane. This enzyme was named endo-beta-N-acetylglucosaminidase HS. Thus, these studies indicate that the properties of the enzyme are distinct from those of known endo-beta-N-acetylglucosaminidase and endo-beta-N-acetylglucosaminidase HS is a novel endo-beta-N-acetylglucosaminidase.
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PMID:Human salivary endo-beta-N-acetylglucosaminidase HS specific for complex type sugar chains of glycoproteins. 834 Apr 28

After a meal rich in plant products, dietary flavonols can be detected in plasma as serum albumin-bound conjugates. Flavonol-albumin binding is expected to modulate the bioavailability of flavonols. In this work, the binding of structurally different flavonoids to human and bovine serum albumins is investigated by fluorescence spectroscopy using three methods: the quenching of the albumin fluorescence, the enhancement of the flavonoid fluorescence, the quenching of the fluorescence of the quercetin-albumin complex by a second flavonoid. The latter method is extended to probes whose high-affinity binding sites are known to be located in one of the two major subdomains (warfarin and dansyl-L-asparagine for subdomain IIA, ibuprofen and diazepam for subdomain IIIA). Overall, flavonoids display moderate affinities for albumins (binding constants in the range 1-15 x 10(4) M(-1)), flavones and flavonols being most tightly bound. Glycosidation and sulfation could lower the affinity to albumin by one order of magnitude depending on the conjugation site. Despite multiple binding of both quercetin and site probes, it can be proposed that the binding of flavonols primarily takes place in subdomain IIA. Significant differences in affinity and binding location are observed for the highly homologous HSA and BSA.
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PMID:Flavonoid-serum albumin complexation: determination of binding constants and binding sites by fluorescence spectroscopy. 1565 91