Search PubMed⌕ Search

Biomedical subjects

S Tsuiki

Publications and source records attributed to S Tsuiki.

At least 73 records · Page 4Linked to original sources
PubMed1980

Purification and subunit structure of a high-molecular-weight phosphoprotein phosphatase (phosphatase II) from rat liver.

1. Phosphatase II is a form of phosphoprotein phosphatase originally found in rat liver extract; it has a molecular weight of 160 000 by gel filtration and is highly active towards phosphorylase alpha. This phosphatase has been purified 1800-fold by using DEAE-cellulos (DE-52), aminohexyl--Sepharose-4B, protamine--Sepharose-4B and Sephadex G-200 chromatography. Throughout the purification steps, the original molecular weight and substrate specificity of phosphatase II were almost perfectly preserved. 2. The product of the final purification step migrated predominantly as a single protein band on non-denaturing gel electrophoresis. Sodium dodecyl sulfate gel electorphoresis revealed that the enzyme contains two types of subunit, alpha and beta, with molecular weights of 35 000 and 69 000, respectively. When treated with 0.2 M 2-mercaptoethanol at -20 degrees C, phosphatase II was dissociated to release the catalytically active alpha subunit. The beta subunit may be catalytically inactive but interacts with the alpha subunit so that phosphatase II becomes much less susceptible than the alpha subunit to inactivation by ATP or pyrophosphate.

Animals↗
PubMed1980

Purification and subunit structure of rat-liver phosphoprotein phosphatase, whose molecular weight is 260000 by gel filtration (phosphatase IB).

1. Phosphoprotein phosphatase IB is a form of rat liver phosphoprotein phosphatase, distinguished from the previously studied phosphoprotein phosphatase II [Tamura et al. (1980) Eur. J. Biochem. 104, 347-355] by earlier elution from DEAE-cellulose, by higher molecular weight on gel filtration (260000) and by lower activity toward phosphorylase alpha. This enzyme was purified to apparent homogeneity by chromatography on DEAE-cellulose, aminohexyl--Sepharose-4B, histone--Sepharose-4B, protamine--Sepharose-4B and Sephadex G-200. 2. The molecular weight of purified phosphatase IB was 260000 by gel filtration and 185000 from S20,W and Stokes' radius. Using histone phosphatase activity as the reference for comparison, the phosphorylase phosphatase activity of purified phosphatase IB was only one-fifth that of phosphatase II. 3. Sodium dodecyl sulfate gel electrophoresis revealed that phosphatase IB contains three types of subunit, namely alpha, beta and gamma, whose molecular weights are 35000, 69000 and 58000, respectively. The alpha subunit is identical to the alpha subunit of phosphatase II. While the beta subunit is also identical or similar to the beta subunit of phoshatase II, the gamma subunit appears to be unique to phosphatase IB. 4. When purified phosphatase IB was treated with 2-mercaptoethanol at -20 degrees C, the enzyme was dissociated to release the catalytically active alpha subunit. Along with this dissociation, there was a 7.4-fold increase in phosphorylase phosphatase activity; but histone phosphatase activity increased only 1.6-fold. The possible functions of the gamma subunit are discussed in relation to this activation of enzyme.

Animals↗
PubMed1980

UDP-N-acetylglucosamine 2'-epimerase of rat hepatoma and its comparison with the enzyme of rat liver.

UDP-N-acetylglucosamine 2'-epimerase was partially purified from Yoshida sarcoma, a strain of rat ascites hepatoma, by (NH4)2SO4 precipitation followed by TEAE-cellulose chromatography. The purified enzyme was inhibited by CMP-N-acetylneuraminic acid to similar extent to partially purified rat liver 2'-epimerase. Although the two enzymes were also similar in Km for UDP-N-acetylglucosamine, they were differentiated by chromatography on TEAE-cellulose, DEAE-Sephadex and hydroxyapatite, tumor enzyme being less tightly bound to these columns than liver enzyme. Similar chromatographic difference was also noted between 2'-epimerases of mouse liver and mouse Ehrlich asites carcinoma.

Animals↗
PubMed1980

Effect of ethanol treatment on high molecular weight phosphoprotein phosphatases of rat liver.

When the crude phosphoprotein phosphatase fraction of rat liver cytosol was treated with 80% aqueous ethanol at room temperature, the activity with phosphorylase alpha as substrate was increased by 110%, but those with glycogen synthase D and phosphohistone were decreased by 53 and 34%, respectively. Chromatography of the ethanol-treated fraction on DE-52 revealed that while phosphoprotein phosphatase IA (Mr=69,000) remained to exist even though it was reduced, phosphatases IB (Mr=-300,00) and II (Mr=160,000) were totally replaced by a new phosphatase form with an approximate molecular weight of 35,000. This low molecular weight form has been designated phosphatase III. When partially purified phosphatases IB and II were separately treated with ethanol, they were converted to phosphatase III. These results suggest that phosphoprotein phosphatases IB and II, but IA, contain phosphatase III as a subunit. Phosphatases IB and II, however, must differ in structure since "IB to III" is accompanied by an increase in phosphorylase phosphatase activity much greater than that for "II to III"

Animals↗
PubMed1979

Metabolism of exogenous N-acetylglucosamine in extracts of rat kidney, liver and hepatoma.

1. The metabolism of exogenous N-acetylglucosamine (GlcNAc) in rat kidney extracts was greatly stimulated by fructose 1,6-diphosphate (Fru-1,6-P2) and to a lesser extent by phosphoenolpyruvate. They served as a generator of ATP. Under these conditions, the majority of metabolized GlcNAc was recovered in the form of glycolytic intermediates. 2. The metabolism of exogenous GlcNAc in rat liver extracts was stimulated by phosphoenolpyruvate but not by Fru-1,6P2. With phosphoenolpyruvate present, most of the metabolized GlcNAc was recovered as sialic acid. 3. The metabolism of exogenous GlcNAc in rat hepatoma (AH-130) extracts was stimulated by Fru-1,6-P2 and to a lesser extent by phosphoenolpyruvate. Even with phosphoenolpyruvate present, the synthesis of sialic acid was extremely small. In these respects, hepatoma extracts resemble kidney extracts rather than those of liver.

Acetylglucosamine↗
PubMed1979

Stabilization and purification of glucosamine 6-phosphate isomerase from rat kidney.

1. Glucosamine 6-phosphate (GlcN-6-P) isomerase of rat kidney was resistant to heating at 50--55 degrees in crude extract but not after several purification steps. GlcN-6-P and N-acetylglucosamine 6-phosphate were found to stabilize the isomerase under these conditions. They also protected the enzyme from tryptic digestion, but only GlcN-6-P was effective against inactivation by p-chloromercuribenzoate. 2. When GlcN-6P isomerase was purified from fresh kidney and kidney stored at -20 degrees, separately and under GlcN-6-P, the two preparations were different in elution profile from a hydroxyapatite column. It was subsequently found that storage of crude extract at -20 degrees resulted in molecular alterations of the enzyme. Prolonged purification appeared to affect the enzyme similarly. The molecular alterations, however, were suppressed if the extract was stored at -70 degrees. 3. These findings have been utilized to develop a procedure, which enables us to purify rat kidney GlcN-6-P isomerase without any molecular alteration and in good yield.

Aldose-Ketose Isomerases↗
PubMed1979

Characterization of rat hepatoma glucosamine 6-phosphate synthase and its relation to liver and fetal forms.

Glucosamine 6-phosphate synthase (EC 5.3.1.19) purified from various rat tissues by a procedure involving chromatography on diethylaminoethyl Sephadex and hydroxylapatite were characterized by means of isoelectric focusing. The non-hepatic isozyme, previously reported to be present in Yoshida sarcoma, has a pI of 4.1 and is distinguished from the hepatic isozyme, with a pI of 5.0. The pI 4.1 form is the major one in all of the fast-growing, transplantable hepatomas studied. Although not detectable in 19-day fetal liver or normal adult liver, the pI 4.1 form has been observed in the whole 12-day fetus and adult brain as almost the sole form of glucosamine 6-phosphate synthase.

Animals↗
PubMed1979

Glucosamine 6-phosphate synthase of regenerating rat liver.

When rats were subjected to partial hepatectomy, glucosamine 6-phosphate synthase (EC 5.3.1.19) of the remaining liver underwent alterations both in activity and in molecular form. To study the molecular alterations, glucosamine 6-phosphate synthase was purified from regenerating as well as control liver and was analyzed by isoelectric focusing. Although control liver exhibited only one form of glucosamine 6-phosphate synthase with a pI of 5.0, sequential and transient appearance of three other forms, with pI values of 4.3, 4.8, and 4.5, respectively, was observed for regeneration liver within 72 hr following partial hepatectomy. Laparotomy, on the other hand, induced in the liver only the pI 4.8 form, and injection of a mixture containing triiodothyronine, amino acids, glucagon, and heparin induced only the pI 4.3 and 4.5 forms. It therefore appears that the pI 4.3 and 4.5 forms, but not the pI 4.8 form, are associated with hepatic DNA synthesis. The pI 4.8 form is induced in the liver in response to surgical stress.

Animals↗
PubMed1978

Characterization of multiple forms of histone phosphatase in rat liver.

By using chromatography on DEAE-cellulose, aminohexyl-Sepharose 4B and Sephadex G-200, rat liver extract was shown to contain at least three fractions, IA, IB and II, of histone phosphatase. Fractions IA and II are probably the same enzymes as the previously described glycogen synthase phosphatase and phosphorylase phosphatase, respectively, but IB exhibits noticeable activities only with phosphohistone as substrate. Approximate molecular weights of 69 000, 300 000 and 160 000 were determined by gel filtration on Sephadex G-200 for IA, IB and II, respectively.

Animals↗
PubMed1976

Stabilization of glucosaminephosphate synthase from rat liver by hexose 6-phosphates. Properties and interconversion of two molecular forms.

Glucosaminephosphate synthase (glucosaminephosphate isomerase (glutamine-forming), EC 5.3.1.19) prepared from rat liver by extraction in the presence of glucose 6-phosphate (Glc-6-P) followed by precipitation with (NH4)2SO4 is susceptible to digestion by trypsin. This enzyme, designated form A, can be converted to tryptic-insusceptible form B upon incubation with Glc-6-P or fructose 6-phosphate (Fru-6-P) at 37 degrees C. The two forms also differ in the degree of activation by dithiothreitol, the degree of inhibition by methyl-glyoxal and the behavior on DEAE-Sephadex and Sephadex G-200 column chromatography. During purification with DEAE-Sephadex followed by hydroxyapatite, form B is converted to form A if Fru-6-P is absent and form A to form B if Fru-6-P is present. The two forms are therefore intercovertible. Under the conditions of purification, form B is more stable than form A, since the purity and yield of the final product are greater with form B than with form A. These findings suggest that the two forms of glucosaminephosphate synthase differ conformationally and that the equilibrium position depends on the concentration of Fru-6-P. Glc-6-P is effective only when it gives rise to Fru-6-P by mediation of glucose-phosphate isomerase.

Animals↗
PubMed1976

Glucosaminephosphate synthase of human liver.

Although human liver contains glucosaminephosphate synthase (glucosaminephosphate isomerase (glutamine-forming), EC 5.3.1.19), its activity is rapidly lost during the course of extraction. The inactivation, however, is largely prevented if the extraction medium contains isopropanol at 1% concentration; using these "stabilized" extracts, the glucosaminephosphate synthase activity of human liver has been shown to be similar to the activity previously reported in rat liver. The enzyme precipitated from these extracts by (NH4)2SO4 is inhibited by UDP-N-acetylglucosamine, the concentration required to produce a half-maximal inhibition being 6 muM. These results seem to be sufficient to postulate that glucosaminephosphate synthase is important for UDP-N-acetylglucosamine synthesis in human liver. In contrast to the rat liver enzyme, the (NH4)2SO4-precipitated human liver enzyme is resistant to trypsin and undergoes no conversion reaction when incubated with glucose 6-phosphate.

Carbohydrate Epimerases↗