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T Miyagi

Publications and source records attributed to T Miyagi.

At least 145 records · Page 8Linked to original sources
PubMed1982

Purification and characterization of beta-galactoside (alpha 2 leads to 6)sialyltransferase from rat liver and hepatomas.

Asialofetuin sialyltransferase from Triton X-100 extracts of rat liver was resolved by phosphocellulose chromatography into two fractions, designated I and II in order of elution. When previously treated with Arthrobacter ureafaciens neuraminidase, fraction I eluted at about the same position as II while no alteration occurred in II. Primary rat hepatomas contained only a single asialofetuin sialyltransferase, identical to fraction I in chromatographic behavior. Transferases I and II were purified to near homogeneity. Transferase II, as well as neuraminidase-treated I, could be sialylated auto-catalytically, indicating that the lack of sialic acid in II is not due to the lack of a sialic-acid-accepting site. Both enzymes formed an (alpha 2 leads to 6)sialylgalactoside linkage with asialo-glycoproteins of the glycosylamine-type and with lactose, and were indistinguishable immunologically. Nevertheless, the transferases exhibited different molecular weights of 37000 (I) and 43000 (II). When heated at 50 degrees C, transferase I lost half its original activity within 20 min while II was scarcely inactivated. Kinetically, transferase I showed three-times higher affinity than II for CMP-N-acetylneuraminic acid and for desialylated plasma membrane. Asialofetuin sialyltransferase was also purified from primary rat hepatoma. The purified enzyme was identical to transferase I in every respect examined. We conclude that hepatomas contain transferase I but lack transferase II.

Animals↗
PubMed1981

Studies on UDP-N-acetylglucosamine : alpha-mannoside beta-N-acetylglucosaminyltransferase of rat liver and hepatomas.

When homogenates of rat liver and hepatomas were centrifuged at 78 000 X g, over 90% of liver N-acetylglucosaminyltransferase assayed with beta-galactosidase- and beta-N-acetylhexosaminidase-treated asialofetuin as acceptor was recovered in the particulate fraction, while as much as 24% of hepatoma transferase was in the supernatant fraction. The particulate transferase solubilized by 0.2% sodium deoxycholate emerged from a DEAE-cellulose column at 0.04 M NaCl (transferase A). The supernatant fractions from all the hepatomas tested contained a second N-acetylglucosaminyltransferase eluted from the column at 0.02 M NaCl (transferase B). Transferase B was absent from liver supernatant fraction. The activities of these transferases toward various acceptors and the effect of beta-N-acetylhexosaminidase on their products suggest that both transferases are UDP-N-acetylglucosamine : alpha-mannoside beta-N-acetylglucosaminyltransferase. Although ovalbumin and glycopeptide V, which was isolated from pronase digest of ovalbumin, were good acceptors, transferase A utilized ovalbumin and glycopeptide V with apparent Km values of 0.44 and 0.33 mM, respectively, whereas the corresponding values for transferase B were 4.5 and 0.050 mM.

Animals↗
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↗
PubMed1975

Carcinofetal alterations in glucosamine-6-phosphate synthetase.

The levels of glucosamine-6-phosphate synthetase in various rat tissues including those undergoing differentiation or regeneration revealed that the enzyme is related to tissue proliferation and differentiation. In the liver upon neoplastic transformation, the level of glucosamine 6-phosphate synthetase rises and the liver form of the enzyme having a pI at 5.0 is replaced by a form with a pI of 4.1. Since the latter form has also been found present in whole embryos (12- and 14-day) and brain, the molecular alterations of glucosamine-6-phosphate synthetase in liver neoplasia can be considered to be carcinofetal.

Aging↗