Hiroaki Tanioka

Dietary response of various key enzymes related to glucose metabolism in normal and diabetic rat liver

Abstract With normal rats, administration of a high glycerol diet for 3 days produces a great increase in the activities of various key enzymes involved in glucose utilization in the liver. These include glucokinase (EC 2.7.1.12), pyruvate kinase (EC 2.7.1.40), glucose-6-phosphate dehydrogenase (EC 1.1.1.49), ATP citrate lyase (EC 4.1.3.8) and acetyl-CoA carboxylase (EC 6.4.1.2). Administration of a high glycerol diet to diabetic animals also causes a marked induction of all these enzymes, except glucokinase and glucose-6-phosphate dehydrogenase, in the liver. The latter two enzymes show little response to glycerol feeding in the diabetic state. The induction of pyruvate kinase nd ATP citrate lyase by glycerol feeding is almost completely abolished by actinomycin D treatment in both normal and diabetic rats. The elevated activities of glucose-6-phosphatase (EC 3.1.3.9) and l -serine dehydratase (EC 4.2.1.13) in diabetic liver are not lowered but rather increase on feeding glycerol. A possible explanation for these results is presented, especially in relation to the action of insulin.

Purification and properties of homogentisate oxygenase from Pseudomonas fluorescens

Summary Homogentisate oxygenase from Pseudomonas ftuorescens adapted to tyrosine has been isolated, purified and crystallized. The crystallized enzyme was homogeneous on ultracentrifugation, and its sedimentation constant was found to be 11.8 S. The molecular weight of the enzyme was calculated to be about 380 000. Like the mammalian liver enzyme, bacterial homogentisate oxygenase requires ferrous iron as a cofactor. For maximal activity, the enzyme requires at least 10 min preincubation with ferrous iron at pH 6.0. The optimal pH is 6.0. Both glutathione and ascorbate are also required for maximal activity at pH 6.0, but only the former is essential at pH 5.4. The Km values are 6 · 10−4 M for homogentisate and 1 · 10−4 M for Fe2+ at pH 6.0. Unlike the mammalian liver enzyme, the bacterial enzyme is fairly stable on aging or storage. p-Chloromercuribenzoate inhibits the enzyme with respect to ferrous iron, but non-competitively with respect to homogentisate. The properties of bacterial homogentisate oxygenase are discussed in comparison with those of the mammalian liver enzyme.

RESPIRATORY CONTROL OF DISPERSED RAT-LIVER CELLS.

Abstract The respiration of dispersed rat-liver cells was measured using an oxygen electrode and conventional manometric techniques. It was found that cellular respiration was regulated by oxidative phosphorylation. This was shown by the marked stimulation of cellular respiration caused by addition of ADP. However, a considerable difference was found in the regulatory patterns of cellular and mitochondrial respiration. At the cellular level, the transition from State 3 to State 4 was gradual, whereas at the mitochondrial level it was abrupt. In addition, cell suspensions maintained their respiratory control in a medium free of polyols. ATP formation in disperesed cells was shown by incorporation of inorganic [ 32 P]phosphate and consumption of added inorganic phosphate.

Mandibular distomolars: A review of the Japanese literature and a report of three additional cases

Abstract Twenty-nine cases of mandibular distomolars have been reported in the Japanese literature. The details of three additional cases are presented.

1-naphthyl acetate esterases in fluids and tissues of jaw cysts.

The activity and electrophoretic mobility of 1-naphthyl acetate esterases in cystic fluids and cystic tissues of ameloblastomas, follicular and apical cysts were examined. The cystic fluids showed lower activities than sera but had very similar patterns on the electrophoretogram. The activity levels of the three kinds of cystic fluids were not statistically significantly different. The fluid esterases may have originated from serum but they were not produced by the cystic lining tissue. Ameloblastoma tissues showed the highest activity per wet weight and per mg protein of the three kinds of cyst lesions (P less than 0.05). On the electrophoretogram, the esterase-I activity constituted 41% of the total activity in ameloblastomas, whereas in follicular cysts and apical cysts the esterase-I activity constituted 32% and 24% of the total activity, respectively.