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Biomedical subjects

H Nakamoto

Publications and source records attributed to H Nakamoto.

At least 127 records · Page 7Linked to original sources
PubMed1986

Light Activation of Pyruvate,Pi Dikinase and NADP-Malate Dehydrogenase in Mesophyll Protoplasts of Maize : Effect of DCMU, Antimycin A, CCCP, and Phlorizin.

Pyruvate,Pi dikinase (PPDK, EC 2.7.9.1) and NADP-malate dehydrogenase (MDH, EC 1.1.1.82) were activated in the light and inactivated following a dark treatment in mesophyll protoplasts of maize. DCMU (up to 33 micromolar), an inhibitor of noncyclic electron transport, inhibited activation of MDH much more strongly than it did PPDK. Antimycin A (6.6-33 micromolar), an inhibitor of cyclic photophosphorylation, inhibited the activation of PPDK (up to 61%), but had little or no effect on activation of MDH. Carbonyl cyanide m-chlorophenylhydrazone (0.2-2 micromolar) and nigericin (0.4 micromolar), uncouplers of photophosphorylation, inhibited activation of PPDK while stimulating the activation of MDH. Phlorizin (0.33-1.7 millimolar), an inhibitor of the coupling factor for ATP synthesis, strongly inhibited activation of PPDK but only slightly effected light activation of MDH. These results suggest that noncyclic electron flow is required for activation of NADP-MDH and that photophosphorylation is required for activation of PPDK.

Journal Article↗
PubMed1986

[von Recklinghausen's disease associated with pheochromocytoma--an autopsy case report and review of 24 cases in the Japanese literature].

A 56-year-old woman was admitted because of vomiting and right hypochondralgia. Since she was 25 years old, she had been sick with neurofibromatosis. Systemic neurofibromatosis with café-au-lait spots, blood hypertension and tenderness on the right hypochondrium were found. Ultrasonic examination revealed a right adrenal mass. Levels of serum catecholamines were elevated. She developed ileus and died of shock from the release of adrenal catecholamines. Postmortem examination showed right adrenal pheochromocytoma. The tumor measured 11.5 X 8 cm and weighed 25 gm. Von Recklinghausen's disease associated with pheochromocytoma is very rare, and only 24 cases have been reported in Japan. We present our case here with a review of the literature.

Adrenal Gland Neoplasms↗
PubMed1985

Pyruvate, pi dikinase in bundle sheath strands as well as in mesophyll cells in maize leaves.

Mesophyll protoplasts and bundle sheath strands were isolated from maize leaves. Light microscopic observation showed the preparations were pure and without cross contamination. Protein blot analysis of mesophyll and bundle sheath cell soluble protein showed that the concentration of pyruvate orthophosphate dikinase (EC 2.7.9.1) is about one-tenth as much in the bundle sheath cells as in mesophyll cells, but about eight times greater than that found in wheat leaves, on the basis of soluble protein. Phosphoenolpyruvate carboxylase (EC 4.1.1.31) was barely detectable in the bundle sheath cells, while ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) and NADP-dependent malic enzyme (EC 1.3.1.37) were exclusively present in the bundle sheath cells and were absent in the mesophyll cells. Whereas pyruvate, Pi dikinase was previously considered localized only in mesophyll cells of C(4) plants, these results clearly demonstrate the presence of appreciable quantities of the enzyme in the bundle sheath cells of the C(4) species maize.

Journal Article↗
PubMed1984

Antiulcer actions in rats of new synthetic polyisoprenoids.

The effects of 3-N,N-dimethylaminopropyl farnesyl acetate (DMFA), N'-geranylpiperazinyl farnesyl acetamide (GPFA) and N'-methylpiperazinyl geranylgeranyl acetamide (MPGA) were studied on gastric secretion, gastric bleeding and gastric mucosubstances in rats. DMFA lowered gastric juice and gastric bleeding, and GPFA increased gastric mucosubstances and decreased gastric bleeding. MPGA showed remarkable effects for all of these tests. Consequently it might be said that MPGA is a useful agent against both aggressive and resistant factors on gastric functions.

Alcian Blue↗
PubMed1983

Control of the activation/inactivation of pyruvate, Pi dikinase from the C4 plant maize by adenylate energy charge, pyruvate, and analogs of pyruvate.

Pyruvate, Pi dikinase, which is localized in the mesophyll chloroplasts of C4 plants, requires a high adenylate energy charge for conversion of the enzyme from the inactive to the active form. The inactivation process is favored by a low energy charge, being maximal at values below 0.7. Pyruvate and analogs of pyruvate, oxamate and oxalate, strongly inhibit the inactivation process at millimolar levels. The results suggest that light activation of the enzyme in vivo may be mediated by an increased adenylate energy charge in the chloroplast. Pyruvate may allow a higher steady-state level of activation to be achieved in vivo by inhibiting inactivation.

Adenine Nucleotides↗
PubMed1983

Influence of Oxygen and Temperature on the Dark Inactivation of Pyruvate, Orthophosphate Dikinase and NADP-Malate Dehydrogenase in Maize.

The influence of oxygen and temperature on the inactivation of pyruvate, Pi dikinase and NADP-malate dehydrogenase was studied in Zea mays. O(2) was required for inactivation of both pyruvate, Pi dikinase and NADP-malate dehydrogenase in the dark in vivo. The rate of inactivation under 2% O(2) was only slightly lower than that at 21% O(2). The in vitro inactivation of pyruvate, Pi dikinase, while dependent on adenine nucleotides (ADP + ATP), did not require O(2).The postillumination inactivation of pyruvate, Pi dikinase in leaves was strongly dependent on temperature. As temperature was decreased in the dark, there was a lag period of increasing length (e.g. at 17 degrees C there was a lag of about 25 minutes) before inactivation proceeded. Following the lag period, the rate of inactivation decreased with decreasing temperature. The half-time for dark inactivation was about 7 minutes at 32 degrees C and 45 minutes at 17 degrees C. The inactivation of pyruvate, Pi dikinase in vitro following extraction from illuminated leaves was also strongly dependent on temperature, but occurred without a lag period. In contrast, NADP-malate dehydrogenase was rapidly inactivated in leaves (half-time of approximately 3 minutes) during the postillumination period without a lag, and there was little effect of temperature between 10 and 32 degrees C. The results are discussed in relation to known differences in the mechanism of activation/inactivation of the two enzymes.

Journal Article↗
PubMed1983

Photosynthetic Characteristics of C(3)-C(4) Intermediate Flaveria Species : I. Leaf Anatomy, Photosynthetic Responses to O(2) and CO(2), and Activities of Key Enzymes in the C(3) and C(4) Pathways.

Four species of the genus Flaveria, namely F. anomala, F. linearis, F. pubescens, and F. ramosissima, were identified as intermediate C(3)-C(4) plants based on leaf anatomy, photosynthetic CO(2) compensation point, O(2) inhibition of photosynthesis, and activities of C(4) enzymes. F. anomala and F. ramosissima exhibit a distinct Kranz-like leaf anatomy, similar to that of the C(4) species F. trinervia, while the other C(3)-C(4) intermediate Flaveria species possess a less differentiated Kranz-like leaf anatomy. Photosynthetic CO(2) compensation points of these intermediates at 30 degrees C were very low relative to those of C(3) plants, ranging from 7 to 14 microliters per liter. In contrast to C(3) plants, net photosynthesis by the intermediates was not sensitive to O(2) concentrations below 5% and decreased relatively slowly with increasing O(2) concentration. Under similar conditions, the percentage inhibition of photosynthesis by 21% O(2) varied from 20% to 25% in the intermediates compared with 28% in Lycopersicon esculentum, a typical C(3) species. The inhibition of carboxylation efficiency by 21% O(2) varied from 17% for F. ramosissima to 46% for F. anomala and were intermediate between the C(4) (2% for F. trinervia) and C(3) (53% for L. esculentum) values. The intermediate Flaveria species, especially F. ramosissima, have substantial activities of the C(4) enzymes, phosphoenolpyruvate carboxylase, pyruvate, orthophosphate dikinase, NADP-malic enzyme, and NADP-malate dehydrogenase, indicating potential for C(4) photosynthesis. It appears that these Flaveria species may be true biochemical C(3)-C(4) intermediates.

Journal Article↗
PubMed1982

Properties of Aspergillus niger catalase.

Catalase from Aspergillus niger was purified to homogeneity as judged from the results of ultracentrifugation and polyacrylamide gel electrophoresis. The enzyme had a molecular weight of 385,000 as estimated from sedimentation measurements. Carbohydrate analyses showed that the catalase was a glycoprotein containing about 8.3% neutral sugar and 1.9% glucosamine. Under denaturing conditions, polyacrylamide gel electrophoresis revealed only one band with a molecular weight of 97,000 daltons in gels stained for either protein or sugar, suggesting that the native enzyme consists of four subunits with covalently bound carbohydrate. In the reaction with inhibitors, A. niger catalase showed lower affinity than the "standard" catalases. The pK values for HCN, HN3, and HF were estimated to be 3.4 (at pH 7.4), 2.3, and 1.5 (at pH 4.2), respectively. In addition, the fungal enzyme reacts with methyl hydrogen peroxide in a very unusual way. Even after the addition of a large excess of the peroxide, only catalase compound I was formed, and compound II did not appear. Using this unique property of A. niger catalase, we obtained CD and MCD spectra of compound I uncontaminated by compound II. The magnitude of the positive CD peak of compound I in the Soret region was about half that of the native enzyme. The MCD spectrum obtained was better resolved than that of bovine liver catalase compound I in the visible region.

Aspergillus niger↗
PubMed1982

Partial characterization of the in vitro activation of inactive pyruvate, pi dikinase from darkened maize leaves.

In vitro activation of dark-inactivated pyruvate, orthophosphate dikinase extracted from maize (Zea mays L. cv. Golden Cross Bantam T51) leaves was examined. The inactive form of the enzyme and orthophosphate behaved kinetically as substrates for the reaction, which was catalyzed by an activating factor. This factor was bound by Blue Dextran Sepharose 4B and could be eluted by KCl at a concentration of 0.5m. The molecular weight of the maize leaf activating factor was about 88,000. Cibacron Blue 3G-A, a reactive moiety of Blue Dextran, inhibited the factor competitively with respect to the concentration of the inactive dikinase with a K(i) of 4.6 micromolar. Adenosine diphosphate and pyrophosphate were also found to be competitive inhibitors of activation, with respect to the inactive dikinase, giving K(i) values of 90 and 140 micromolar, respectively. Adenosine, other nucleotide diphosphates, and dinucleotides gave little or no inhibition of activation. These results suggest the association of a nucleotide, presumably nucleotide diphosphate, with the inactive form of pyruvate, orthophosphate dikinase.

Journal Article↗