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Biomedical subjects

Y Shimamori

Publications and source records attributed to Y Shimamori.

At least 37 records · Page 2Linked to original sources
PubMed1990

Human placental carboxypeptidase M is anchored by a glycosyl-phosphatidylinositol moiety.

Basic carboxypeptidase activity was released from human placental membranes on treatment with phosphatidylinositol-specific phospholipase C of Bacillus thuringiensis. The enzyme was successively purified to homogeneity by SDS-polyacrylamide gel electrophoresis. The molecular nature and some catalytic properties of the purified enzyme revealed that it is identical with recently described basic carboxypeptidase M (R.A. Skidgel et al. J. Biol. Chem. 264 (4) 1989 2236-2241).

Female↗
PubMed1989

Aminopeptidases in human retroplacental sera: purification and characterization of two enzymes.

Ten different maternal serum samples were analyzed for the hydrolysis of S-Bz-Cys-pNA (substrate for CAP) and Ala-pNA. The results showed clear differences in the activities in individual sera. Similar S-Bz-Cys-pNA hydrolysis activity was detected for all sera. However, Ala-pNA hydrolysis activity differed remarkably. Serum exhibiting low Ala-pNA hydrolysis activity contained only CAP, and that exhibiting high Ala-pNA hydrolyzing activity contained CAP and AAP. The two aminopeptidases were independently purified to a homogeneous state through the same purification procedures and some of their biochemical properties were compared. The enzymes were quite different with respect to molecular mass, the substrate specificities for some aminoacyl-pNA substrates, and the effects of inhibitors. Among various natural peptides tested for hydrolysis, the enzymes hydrolyzed Met-enkephalin most rapidly, but their modes of action were different. Furthermore, only CAP degraded oxytocin and AAP exhibited a high kinin-converting activity.

Aminopeptidases↗
PubMed1988

Human placental dipeptidyl aminopeptidase III: hydrolysis of enkephalins and its stimulation by cobaltous ion.

The degradation of enkephalin and related peptides by highly purified dipeptidyl aminopeptidase III (EC 3.4.14.4) was studied. The enzyme releases the N-terminal dipeptide units from substrates greater in length than the tetrapeptide. The enzyme exhibits an optimum of pH 7.5, Km of 81 microM and Vmax of 0.043 mumole/min for Leu-enkephalin. Its activity was markedly stimulated by Co2+, with both the Km and Vmax being increased. Among the enkephalin-related peptides examined, des-Tyr1-Leu-enkephalin was the most rapidly hydrolyzed with Co2+, but only slight stimulation was observed with Co2+.

Cations, Divalent↗
PubMed1987

Purification and characterization of a membrane-bound neutral endopeptidase from human placenta.

A membrane-bound neutral endopeptidase which hydrolyzes Suc-(Ala)3-pNA to succinyl dialanine and Ala-pNA has been purified from human placenta. The enzyme was solubilized from membranes with DOC and papain, and was purified about 5000-fold by successive chromatographies on Sephadex G-200, DEAE-Sephacel, butyl-Toyopearl 650, and Sephacryl S-300. It was found to be homogeneous on SDS-polyacrylamide gel electrophoresis and to have a molecular weight of about 70,000. It was strongly inhibited by phosphoramidon, thiorphan, and metal-chelating agents, but was not affected by most other protease inhibitors. These findings indicate that it can be classified as a phosphoramidon-sensitive neutral endopeptidase. With biologically active peptides as substrates, the enzyme preferentially cleaved the bonds at the amino side of hydrophobic amino acid residues. The physiological significance of this enzyme is discussed with reference to the placental barrier.

Cell Membrane↗
PubMed1987

Purification and characterization of thiol aminopeptidase from the cytosolic fraction of human placenta.

A thiol-dependent aminopeptidase was purified from the cytosolic fraction of human placenta. The purified enzyme consisted of a single polypeptide chain with a mol wt of 95,000. The enzyme was most active in the neutral region with Ala-pNA as substrate, and the activity was increased about 20-fold in the presence of some -SH compounds. The results of substrate specificity studies indicated that the enzyme hydrolyzes bonds involving the amino groups of neutral and basic amino acid residues. However, higher thiol-dependent activity was only detected with neutral ones. The enzyme was strongly inhibited by microbial aminopeptidase inhibitors, puromycin, o-phenanthroline, and sulfhydryl reactive-reagents. As to several naturally occurring peptides tested, the enzyme showed N-terminal Tyr-releasing activity toward enkephalins and kinin-converting activity.

Aminopeptidases↗
PubMed1984

Purification of a membrane-bound neutral endopeptidase from rat kidney and its activation by polyamines.

An endopeptidase which cleaves succinyl trialanine p-nitroanilide (Suc(Ala)3-pNA) into succinyl dialanine and alanine p-nitroanilide (Ala-pNA) was solubilized from a microsomal membrane fraction of rat kidney with Nonidet P-40 following treatment with 1 M KCl and Brij 35. The solubilized enzyme was purified to homogeneity by DEAE-Sephadex chromatography, Sepharose CL-6B gel filtration and sucrose gradient centrifugation. The final enzyme preparation had a specific activity of 1.69 mumol/min/mg protein, representing about 140-fold purification over the starting membrane. The enzyme hydrolyzes Suc(Ala)3-pNA with a Km value of 0.28 mM and a Vmax value of 1.3 mumol/min. The molecular weight of the undenatured enzyme was estimated to be 360,000 by gel filtration on a Sepharose CL-6B column and that of the denatured enzyme to be 92,000 by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis, revealing the presence of a single polypeptide chain. The enzyme was markedly activated by polyamines, producing increases in the values of both Km and Vmax. Comparatively less activation was found in the presence of some monovalent cations and Ca2+. The activation by polyamines was inversely proportional to the concentration of monovalent cations, but Ca2+ and polyamines seemed to stimulate additively.

Aminopeptidases↗
PubMed1983

Activated carbon beads for the removal of highly albumin-bound species.

Activated carbon beads in which 5% activated carbon powder was embedded in 4% agarose were prepared by the emulsion technique. The column of the beads was demonstrated to effectively remove salicylic acid, warfarin, and long-chain fatty acids from solutions containing albumins by either zonal or frontal analysis under the condition of 0.1 M NaCl, pH 3.0 (HCl). The beads were also demonstrated to purify a commercial human serum albumin preparation from residual fatty acids. The beads would be of value in many biochemical purification processes in which activated carbon is employed.

Adsorption↗
PubMed1982

Binding capacities of human serum albumin monomer and dimer by continuous frontal affinity chromatography.

Human serum albumin monomer and dimer obtained by fractionation of a commercial preparation were immobilized on CH-Sepharose 4B by covalent coupling. For salicylic acid, warfarin, phenylbutazone, mefenamic acid, sulphamethizole and sulphonylureas, the binding capacities of the monomer and dimer were compared by continuous frontal affinity chromatography. The salicylate-binding capacities of both monomer and dimer were essentially retained upon immobilization. For these drugs, the dimer showed only about 10-30% less capacity per monomeric unit than that of the monomer, the reduction being associated for most drugs with the intrinsic binding constant rather than with the number of binding sites.

Chromatography, Affinity↗
PubMed1980

Mutual displacement interactions in the binding of two drugs to human serum albumin by frontal affinity chromatography.

A continuous frontal analysis chromatographic method was developed for studying the simultaneous binding of two drugs or ligands with an immobilized macromolecule. The usefulness of this method was demonstrated in the interactions of sulphamethizole and salicylic acid with human serum albumin (HSA). The mutual inhibitory effect on the binding of one drug of the presence of the other was directly shown to be due to displacement of the bound drug from HSA by the other. On the basis of a double-reciprocal plot analysis, these two drugs are interpreted as competing for the same primary binding sites.

Binding, Competitive↗
PubMedDate not supplied

Magnetite (Fe3O4) microcapsules prepared using a glass membrane and solvent removal.

Fine magnetite powders dispersed in polymer solution were encapsulated from an oil-in-water emulsion prepared by an emulsification process employing a porous glass membrane and subsequent evaporation of the solvent. Styrene-based copolymers were dissolved in a magnetic fluid, and then continuously pushed through the pores of glass membrane into the aqueous phase, which had dissolved polyvinyl alcohol (PVA) and sodium dodecyl sulphate (SDS) as a mixed stabilizer. P(styrene-co-acrylic acid) (PS-AA), P(stryrene-co-butyl acrylate) (PS-BA) and styrene-butadiene rubber (SBR) were dissolved in the specially ordered magnetite fluid (25 wt% magnetite dispersed in toluene) separately or as a mixture, and uniform droplets suspending the magnetic particles were obtained. After the evaporation of toluene, PS-AA capsules retained a spherical shape and uniformity, whereas PS-AA/PS-BA capsules revealed a creased surface and broader size distribution. The microcapsules entrapped 30-40 wt% of magnetite, and the encapsulation yield of magnetite was 20-40%. Glass membranes with 9.5, 5.25 and 1.42 microm pore size were employed and 5-40 microm microcapsules were obtained depending on the pore size. When magnetite suspended in chloroform was used, magnetite capsules with broader size distributions were obtained because of the sticking of the droplets to the membrane wall. The advantage of the membrane emulsification which provides uniform sized droplets was lost.

Capsules↗