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Biomedical subjects

E Ito

Publications and source records attributed to E Ito.

At least 325 records · Page 18Linked to original sources
PubMed1981

Structure of polygalactosamine produced by Aspergillus parasiticus.

The structure of polygalactosamine purified from the culture fluid of Aspergillus parasiticus AHU 7165 was studied. Partial acid hydrolysis of this polysaccharide, in which 55 to 65% of the monosaccharide residues were N-unsubstituted, gave a series of galactosamine oligosaccharides (dimer to hexamer) in a good yield. From the data on analyses of the polysaccharide and its oligosaccharides by gel filtration, periodate oxidation, methylation, and proton NMR measurement, the polysaccharide was characterized as a linear chain of alpha (1-4)-linked galactosamine residues. The N-unsubstituted galactosamine residues are probably distributed in a random fashion over the polysaccharide chain.

Acetylgalactosamine↗
PubMed1981

The effects of naturally occurring bisdihydrofuran ring-containing mycotoxins on cultured chick embryonal hepatocytes.

The cytotoxicity of 16 naturally occurring mycotoxins which contain the bisdihydrofuran ring was evaluated by electron-microscopy and radioautography in a primary culture of chick embryonal hepatocytes. A series of nucleolar changes occurred, including the appearance of microsegregation (stage I), concentration of nucleolar structure (stage II), formation of macrosegregation, fragmentation of nucleoli, and the appearance of homogeneously granular nucleoli (stage III). These nucleolar changes correlate well with the inhibition of RNA synthesis calculated from the results of radioautography. The compounds containing a 2,3-double bond in the bisdihydrofuran ring were most toxic. However, it was clear that there was a remarkable difference between mycotoxins of angular type (group A) and those of linear type (group C). Therefore, not only the active site in the molecule but also the shape of the molecule may play an important role in the cytotoxicity of these mycotoxins.

Aflatoxins↗
PubMed1980

Enzymatic deacetylation of N-acetylglucosamine residues in cell wall peptidoglycan.

An enzyme which catalyzes the hydrolysis of acetamido groups of N-acetylglucosamine residues in cell wall peptidoglycan was found in the supernatant and 20,000 X g pellet fractions of Bacillus cereus. Autolysis of the latter fraction resulted in solubilization and activation of the deacetylase. Among various bacteria, strains of B. cereus which contain high proportions of N-unsubstituted glucosamine residues in their cell wall peptidoglycan components are particularly rich in the deacetylase. The peptidoglycan deacetylase is distinguishable from N-acetylglucosamine-6-phosphate deacetylase [EC 3.5.1.25] on the basis of their cellular distribution and chromatographic behavior. The rate of reaction of the deacetylase with (N-acetylglucosaminyl-N-acetylmuramic acid)3 [abbreviated as (GlcNAc-MurNAc)3] is less than 1/100 of that with peptidoglycan, while the enzyme is inactive towards (GlcNAc-MurNAc)2, GlcNAc-MurNAc, and monomeric N-acetylglucosamine derivatives. The enzyme also deacetylates partially O-hydroxyethylated chitin. The concentrations of peptidoglycan and partially O-hydroxyethylated chitin required for half-maximum activities were found to be 0.29 and 6.9 mg per ml (or 0.17 and 20 mM with respect to N-acetylglucosamine residues), respectively. The occurrence of this enzyme accounts for the formation of cell wall peptidoglycan N-unsubstituted at the glucosamine residues.

Acetylglucosamine↗
PubMed1980

Separation and characterization of an autolytic endo-beta-glucosaminidase from Bacillus cereus.

1. An autolytic endo-beta-glucosaminidase, capable of cleaving the glycoside linkages of N-unsubstituted glucosamine in the glycan moiety of cell wall peptidoglycan, was purified 470-fold from a salt extract of the 2,000 x g precipitate fraction obtained after sonication of a lysozyme-resistant strain of Bacillus cereus. The properties of this enzyme were studied. 2. The purified enzyme preparation was also active towards the glycan chain of fully N-acetylated cell wall peptidoglycan. 3. The endo-beta-glucosaminidase was inactive towards the cell wall peptidoglycan unless the peptide portion of this polymer was removed either by the action of N-acetylmuramyl-L-alanine amidase or by the treatment with alkali in aqueous dimethyl sulfoxide. 4. Studies on the action of this enzyme towards chemically modified glycans revealed that the carboxyl groups of muramic acid residues are indispensable to a substrate for this enzyme.

Amidohydrolases↗
PubMed1980

Bacillus cereus autolytic endoglucosaminidase active on cell wall peptidoglycan with N-unsubstituted glucosamine residues.

An autolytic glycosidase from a lysozyme-resistant strain of Bacillus cereus capable of cleaving the glycosidic linkages of N-unsubstituted glucosamine in the cell wall peptidoglycan was studied. This glycosidase activity, together with N-acetylmuramyl-L-alanine amidase activity, was found in an autolytic enzyme preparation obtained from the 20,000 x g precipitate fraction by means of autolysis followed by ammonium sulfate fractionation. The major saccharide fragments resulting from digestion of the untreated, non-N-acetylated, cell wall peptidoglycan of B. cereus with the autolytic enzyme preparation were identified as N-acetylmuramyl-glucosamine and its dimer. The peptidoglycan N-acetylated with acetic anhydride could also be digested with the same enzyme preparation, giving N-acetylmuramyl-N-acetylglucosamine and its dimer as the major saccharide fragments.

Bacillus cereus↗
PubMed1979

Anomeric configuration of N-acetylglucosaminyl phosphorylundecaprenols formed in Bacillus cereus Membranes.

The structural difference was studied between two N-acetylglucosaminyl phosphorylundecaprenols formed by incubation of Bacillus cereus membranes with UDP-N-acetylglucosamine. On the treatment with 50% phenol, the major one of these glycolipids (Lipid 1) yielded a saccharide phosphate, while the other (Lipid 2) yielded N-acetylglucosamine along with a saccharide phosphate. The saccharide phosphates from Lipids 1 and 2 were identified as alpha-N-acetylglucosamine 1-phosphate and its beta-anomer, respectively, based on their susceptibility to acid, alpha- and beta-N-acetylglucosaminidases, and UDP-N-acetylglucosamine pyrophosphorylase. Thus, it seems most probable that Lipids 1 and 2 were alpha- and beta-N-acetylglucosaminyl phosphorylundecaprenols, respectively.

Bacillus cereus↗
PubMed1979

A pathway of polygalactosamine formation in Aspergillus parasiticus: enzymatic deacetylation of N-acetylated polygalactosamine.

1. An enzyme which hydrolyzes the acetamido groups of N-acetylgalactosamine residues in N-acetylated polygalactosamine was found in the supernatant fraction of Aspergillus parasiticus AHU 7165, a polygalactosamine-producing strain. 2. N-Acetylated polygalactosamine was used as a substrate in the purification and characterization of this enzyme. A 140-fold purification was obtained by means of ammonium sulfate fractionation followed by chromatography on carboxymethylcellulose and DEAE-cellulose. 3. The enzyme releases about 60-70% of the acetyl groups of N-acetylated polygalactosamine, giving a product with free amino groups. Whereas the enzyme also deacetylates oligosaccharides with 14 or more N-acetylgalactosamine units at a rate similar to that of deacetylation of the polymer, it deacetylates shorter oligosaccharides (trimer to hexamer of N-acetylgalactosamine) much more slowly and is virtually inactive toward disaccharide. Deacetylation can not be detected with bacterial cell wall peptidoglycan, N-acetylated heparin, partially O-hydroxyethylated chitin or monomeric N-acetylgalactosamine derivatives as substrates. 4. This enzyme shows double pH optima of 5.3 and 9.3. The Km value for N-acetylated poly-galactosamine is 0.15 g/l (or 0.54 mM with respect to monosaccharide residues). 5. The occurrence of this enzyme may account for the formation of polygalactosamine with free amino groups.

Acetylgalactosamine↗
PubMed1978

Formation and function of N-acetyloglucosamine-linked phosphoryl- and pyrophosphorylundecaprenols in membranes from Bacillus cereus.

Membranes from Bacillus cereus AHU 1356 incorporated radioactivity from UDP-N-acetyl[14C]glucosamine into three alkaline-stable and acid-labile lipids which were extracted into chloroform:methanol (2:1) and separated from each other by thin layer chromatography on silica gel plates. The major labeled lipid (Lipid 1) and a minor one (Lipid 2) were identified as N-actetylglucosaminyl phosphorylundecaprenol from several analytical criteria involving mass spectral data and from reversal of their formation by UDP. These two lipids appear to differ in geometry of their polyprenol moieties. The third labeled lipid (Lipid 3) was identified as N-acetylglucosaminyl pyrophosphorylundecaprenol. Antibiotic 24010, a tunicamycin-like antibiotic, at 1 microgram/ml was found to inhibit almost completely the formation of Lipid 3, whereas it inhibited the formation of Lipid 1 much more weakly and rather enhanced the formation of Lipid 2. Radioactivity was also incorporated into a polymer from UDP-GlcNAc and from Lipid 3. UDP-N-acetylmannosamine, UDP-N-acetylgalactosamine, and UDP-glucose supported the incorporation. Antibiotic 24010 strongly inhibited the incorporation of radioactivity from UDP-GlcNAc into polymer, whereas it did not affect the incorporation from Lipid 3. Thus, it is concluded that N-acetylglucosaminyl pyrophosphorylundecaprenol serves as a precursor in the synthesis of a polymer presumed as the cell wall polysaccharide of this bacterial strain.

Acetylglucosamine↗
PubMed1978

UDP-N-acetylglucosamine-glycoprotein N-acetylglucosaminyltransferase in regenerating rat liver.

The assay condition for N-acetylglucosaminyltransferase activities in rat liver microsomal fraction was developed. The enzyme activities towards endogenous acceptors within 48 h after partial hepatectomy were lower than in controls, exceeding the control level by 96 h, and then higher than in controls up to 240 h after the operation. The changes in N-acetylglucosaminyltransferase activities towards exogenous acceptor (UDP-2-acetamido-2-deoxy-D-glucose: glycoprotein 2-acetamido-2-deoxy-D-glucosyltransferase, EC 2.4.1.51) were consistent with those in the enzyme activities towards endogenous acceptors at 144 h, but not at 48 h, after the operation. The contents of protein and the levels of protein-bound hexosamine in the liver microsomes were decreased at early period of liver regeneration. These results suggest that the acceptor capacity of liver microsomal proteins is diminished during first 48 h of the regeneration. This may be responsible for the decreased transfer of the amino sugar to nascent glycoproteins. However, the enzyme activity was enhanced at 144 h and the level of endogenous acceptors may increase.

Animals↗
PubMed1978

Enzymatic formation of uridine diphosphate N-acetyl-D-mannosamine.

An enzyme that catalyzes the interconversion of UDP-N-acetyl-D-glucosamine and UDP-N-acetyl-D-mannosamine was purified about 700-fold from the supernatant fraction of Bacillus cereus, and the properties of this enzyme were studied. This enzyme was not stimulated by NAD+, NADH, or any metal ions. The optimum pH was between 7.5 and 8.0. At equilibrium of the reaction, the ratio of UDP-N-acetylglucosamine to UDP-N-acetylmannosmaine was about 9:1. The enzyme was inactive toward free N-acetylhexosamines, their phosphate esters, UDP-glucose, and UDP-N-acetylgalactosamine. A stimulatory role of UDP-N-acetylglucosamine was demonstrated. In the reaction with UDP-N-acetylglucosamine, the rate as a function of substrate concentration showed a sigmoidal relationship with a Hill coefficient of 1.8 and an apparent Km value for UDP-N-acetylglucosamine of 1.1 mM. The reverse reaction with UDP-N-acetylmannosamine required the presence of UDP-N-acetylglucosamine. The UDP-N-acetylglucosamine concentration required for half-maximal activation was about 0.5 mM. The apparent Km for UDP-N-acetylmannosamine measured in the presence of 0.5 mM UDP-N-acetylglucosamine was 0.22mM. Other nucleotides or hexosamine derivatives were not stimulatory. The same activity was found in cell extracts from several bacterial species.

Bacillus cereus↗