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S Maguchi

Publications and source records attributed to S Maguchi.

24 records · Page 2Linked to original sources
PubMed1988

Elevated activity and increased mannose-6-phosphate in the carbohydrate moiety of cathepsin D from human hepatoma.

A significant elevation of cathepsin D activity was observed in six human hepatoma tissues as compared to 12 normal human livers. In isoelectric focusing experiments, cathepsin D purified from normal liver exhibited three different forms, with isoelectric points of 5.6, 6.1, and 6.7, while cathepsin D purified from hepatoma contained another five to six more acidic forms in addition to the forms observed in normal liver cathepsin D. When the tumor enzyme was treated with endo-beta-N-acetylglucosaminidase H followed by isoelectric focusing, the acidic components disappeared and were converted to forms identical to those of the normal liver cathepsin D. Determination of the mannose-6-phosphate content showed that hepatoma cathepsin D contains twice as much mannose-6-phosphate as normal liver cathepsin D. Peptide mapping and amino acid analysis showed that the protein moiety of cathepsin D from hepatoma is almost identical with that from normal liver. These findings indicate that the appearance of acidic variants in hepatoma cathepsin D is mainly due to changes in the oligosaccharide chains of the enzyme, which are closely associated with the increase of mannose-6-phosphate in the tumor enzyme.

Carcinoma, Hepatocellular↗
PubMed1988

[Tumor-associated impairment of the processing of hepatoma cathepsin D].

Cathepsin D was purified to apparently homogeneous form from normal human liver and hepatoma. The purified enzyme could not be distinguished between normal liver and hepatoma in terms of specific activity, subunit composition, antigenicity, amino acid composition and tryptic peptides. However, the hepatoma enzyme exhibited more charge heterogeneity to give multiple acidic variant forms which were devoid or much less in the normal liver enzyme. When the hepatoma enzyme was treated with endo-beta-N-acetylglucosaminidase H, the acidic variant forms disappeared and were converted into forms identical to those of normal liver. The content of mannose-6-phosphate in the hepatoma enzyme was twice as much as that in the normal liver enzyme. Thus, charge heterogeneity found in hepatoma cathepsin D is ascribed to increased phosphorylation on oligosaccharides bound to the enzyme, most probably due to cancer-associated, impaired processing in carbohydrate moiety. A significant elevation of cathepsin D activity per tissue proteins was observed in hepatoma as compared to normal liver. In contrast, true specific activity per cathepsin D protein in hepatoma was significantly lowered than that of normal liver. The lower true specific activity in hepatoma tissue may be attributed to an increased content in an inactive, large-molecular precursor form of the enzyme.

Amino Acids↗
PubMed1987

Glycation and inactivation of human Cu-Zn-superoxide dismutase. Identification of the in vitro glycated sites.

The nonenzymatic glycosylation (glycation) of Cu-Zn-superoxide dismutase led to gradual inactivation of the enzyme (Arai, K. Iizuka, S., Tada, Y., Oikawa, K., and Taniguchi, N. (1987) Biochim. Biophys. Acta 924, 292-296). The purified superoxide dismutase from human erythrocytes comprises both glycated and nonglycated forms. The nonglycated Cu-Zn-superoxide dismutase was isolated by boronate affinity chromatography. Incubation of the nonglycated superoxide dismutase with D-[6-3H]glucose in vitro resulted in the gradual accumulation of radioactivity in the enzyme protein, and Schiff base adducts were trapped by NaBH4. The sites of glycation of the superoxide dismutase were identified by amino acid analysis after reverse-phase high performance liquid chromatography of the trypsin-treated peptides. Lysine residues, i.e. Lys3, Lys9, Lys30, Lys36, Lys122, and Lys128, were found to be glycated. Three of the glycated sites lie in Lys-Gly, two in Lys-Ala, and one in Lys-Val. The inactivation of the superoxide dismutase on the glycation is due mainly to the glycation of Lys122 and Lys128, which are supposed to be located in an active site liganding loop. The remaining five sites, such as Lys-Glu, Lys-Asp, Lys-His, and Lys-Thr are relatively inactive as to the formation of either a Schiff base or an Amadori adduct.

Amino Acid Sequence↗