Biomedical subjects

S Sagisaka

Publications and source records attributed to S Sagisaka.

10 recordsLinked to original sources

PubMed2001

Major isoforms of starch branching enzymes in premature seeds of kidney bean (Phaseolus vulgaris L.).

Developing seeds of the kidney bean (Phaseolus vulgaris L.) contain several isoforms of starch branching enzymes. Two of them, KBE1 and KBE2, which are the major forms in the premature seeds, were purified as a single band of protein on SDS-PAGE and native PAGE by chromatographies on DEAE-Sepharose, Bio-Gel P-200, and amylose-binding Sepharose 6B. The enzymes had similar pH optimum (7.0), pH stability (7.0-9.5), temperature optimum (25-30 degrees C), and temperature stability (up to 40 degrees C). Additionally, both were inhibited by various divalent metal ions and activated by citrate. Finally, though their N-terminal amino acid sequences were identical, their molecular masses and affinities for amylose differed; 80 kDa and 1.27 mM for KBE1 and 77 kDa and 0.74 mM for KBE2.

1,4-alpha-Glucan Branching Enzyme↗

PubMed1992

A cold environment is a prerequisite for formation of "plastid initials" in winter buds of poplar.

The "plastid initial," the presumed precursor of eoplasts and proplastids, is present in the cells of the apical meristem of winter buds of poplar (Populus euramericana). The formation of the plastid initial in the cells of winter buds is initiated soon after the breaking of the innate or resting stage of dormancy, even in winter under nongrowing conditions in mid-January or early February. From this stage to March, the conglomeration of the plastid initial and the formation of prolamellar bodies is evident. In contrast to the poplar samples kept outdoors, the cells of the apical meristem of the indoor winter buds did not show any indication of the formation of the plastid initial and the buds of the latter sample did not flush even at the end of May. These results suggest that the sequence of reactions involved in the onset of regrowth may be closely related to the formation of the plastid initial.

Journal Article↗

PubMed1992

Metabolic response to treatment with cold, paraquat, or 3-amino-1,2,4-triazole in leaves of winter wheat.

We treated leaves of winter wheat (Triticum aestivum L.) with cold, paraquat, or 3-amino-1,2,4-triazole and compared the responses. We assayed the activities of glucose-6-phosphate dehydrogenase, catalase, dehydroascorbate reductase and ascorbate free radical reductase and levels of hydrogen peroxide, glucose-6-phosphate, fructose-6-phosphate, ascorbate, dehydroascorbate, reduced and oxidized glutathione. With any of the three treatments, contents of cellular peroxides and hexose phosphates were raised. The content of ascorbate was lowered markedly by paraquat treatment, which produces active oxygen species, whereas such a decrease did not occur in other two treatments. When the plants were treated with 3-amino-1,2,4-triazole, which is a specific inhibitor of catalase, the content of oxidized glutathione increased severalfold. The glucose-6-phosphate dehydrogenase activity increased with all three treatments, but it decreased after glyphosate treatment, which does not stimulate the formation of peroxides. The activities of catalase and dehydroascorbate reductase were increased by the treatment of cold and paraquat, while 3-amino-1,2,4-triazole did not affect the dehydroascorbate reductase activity. The activity of ascorbate free radical reductase increased after treatment by paraquat only.

Amitrole↗

PubMed1991

Abrupt increase in the level of hydrogen peroxide in leaves of winter wheat is caused by cold treatment.

After cold treatment of seedlings of winter wheat (Triticum aestivum L.), levels of hydrogen peroxide in the leaves were measured. The concentration of hydrogen peroxide increased to about three times the control level within a few minutes, and returned to the normal level in 15 to 20 minutes. The elevated level of hydrogen peroxide was found to be equivalent to 1.5 micromoles per gram fresh weight tissues of leaves.

Journal Article↗

PubMed1987

An immediate and steep increase in ATP concentration in response to reduced turgor pressure in Escherichia coli B.

Osmotic treatment with sodium chloride of Escherichia coli B growing in the logarithmic phase induced an immediate increase in ATP concentration in response to increased concentrations of added solute in its growth medium in the first 10 min of the addition. After that, ATP concentration decreased gradually. Sodium arsenate and potassium fluoride almost abolished the ATP increase. The time course of the increase was quite different from that of cells treated with inhibitors of protein synthesis. The osmotic treatment did not decrease the viability of cells. In addition, there was no degradation of RNA by 5 min after sodium chloride addition, and, further, the lag time of ATP increase was extended by an inhibitor of nucleotide synthesis. These results indicated that a major fraction of the stress-increased ATP resulted from de novo synthesis, and that it was mainly dependent upon the reaction of substrate-level phosphorylation, which is regulated by turgor pressure.

Adenosine Triphosphate↗

PubMed1980

Occurrence of nicotinamide adenine dinucleotide phosphatelinked glyoxylate reductase in nonphotosynthetic xylem tissue of perennials.

Xylem extracts of poplar tree contained glyoxylate reductase specific for NADPH. By isoelectric focusing in the pH ranges 3.5 to 10 or 4 to 6, the enzyme exhibited a single peak of activity at pH 5.4. The enzyme showed essentially no activity toward hydroxypyruvate, pyruvate, or NADH. The reaction was optimal at pH 6.0 in phosphate buffer and the activity profile exhibited a sharp and narrow pH profile with half-maximal velocities at about pH 7.0. The K(m) of the enzyme for glyoxylate was 0.11 millimolar. The xylem tissue of poplar tree exhibited high levels of enzyme activity (30 micromoles per gram dry weight per hour) even in the wintering stage and a slight change in activity occurred in spring and fall at the time when metabolism transition occurs.

Journal Article↗

PubMed1976

The Occurrence of Peroxide in a Perennial Plant, Populus gelrica.

A large amount of peroxide was found in twigs of poplar, Populus gelrica, which was grown in the field under natural conditions. The peroxide found in xylem and living bark was about 1.2 and 0.5 mumoles per gram dry weight sample, respectively, and served as a substrate both for catalase and cytochrome c peroxidase.

Journal Article↗

PubMed1974

Effect of low temperature on amino Acid metabolism in wintering poplar: arginine-glutamine relationships.

Analyses of free amino acids in poplar (Populus gelrica) were carried out throughout a year to see the effect of low temperature on a system regulating amino acid metabolism in the tree. The results indicated that during the wintering phase arginine was the major amino acid both in bark and xylem, particularly in xylem, and that at the time of budding and growing glutamine and glutamate became dominant. Changes in the relative levels of glutamine (plus glutamate) and arginine to the total amino acids of the alpha-ketoglutarate family indicated the presence of a regulatory system annually controlling the synthesis between glutamine (plus glutamate) and arginine. The system appeared to be governed and sensitized by low temperatures. Neither a transition of the synthesis from arginine to glutamine (plus glutamate) nor budding occurred in the poplars which spent the winter months in a greenhouse.

Journal Article↗

PubMed1974

Transition of metabolisms in living popular bark from growing to wintering stages and vice versa: changes in glucose 6-phosphate and 6-phosphogluconate dehydrogenase activities and in the levels of sugar phosphates.

Activities of glucose 6-phosphate, 6-phosphogluconate, and isocitrate dehydrogenases, together with intermediate levels of the glycolytic pathway and the pentose phosphate cycle, were measured throughout a year in the living bark of poplar (Populus gelrica). Shoots, immediately after budding (early May), contained very high levels of the three enzyme activities, which fell gradually by early or mid-July to a level, roughly equivalent to budding (May) or growing (July) 2-year-old twigs. In September, the former two dehydrogenase activities of the new shoots and 2-year-old twigs began to rise, while the latter activity started to decrease. The rise of the two dehydrogenase activities continued until late November (or early December). The high level of the two dehydrogenase activities lasted until early in April of the following year and then the decrease in the activities began prior to the onset of budding, reaching a low, basal level in early May. The profile of changes in the two dehydrogenase activities appeared to coincide with the increase and decrease of soluble proteins.Normal concentrations of total hexose phosphates in the glycolytic pathway plus 6-phosphogluconate were found to be 288 to 895 mumoles/kilogram dry weight. During the metabolism transition (September and April), a transient and striking increase of 6-phosphogluconate was observed. In September, 6-phosphogluconate reached a level on the order of 10(-4)m and was 4 times that of fructose 6-phosphate. The increase in 6-phosphogluconate coincided with the increase in the glucose 6-phosphate dehydrogenase activity. Coincidentally, with the change of 6-phosphogluconate level, a large deviation of the in vivo ratio of fructose 6-phosphate to glucose 6-phosphate from the known equilibrium constant was observed, showing the relation of pentose phosphate cycle enzyme activity to the control of glycolysis. The ratio of glucose 6-phosphate to glucose 1-phosphate deviated from that predicted. These ratios fluctuated throughout the year and were affected by the growth phases. The levels of pentose phosphate cycle metabolites, except for 6-phosphogluconate, in the bark were extremely low.The level of inorganic phosphate in the living bark throughout the year was dependent upon the growth phases, suggesting the presence of a regulatory mechanism to maintain inorganic phosphate at a given level as the growth phase changed.Sugar phosphate levels of popular twigs or potato tubers (Solanum tuberosum) remained constant after they were stored for 2 weeks at low temperatures, whereas in sweet potato roots (Ipomoea batatas), the level rose to about 9-fold of the control, indicating the presence of a strict regulatory system for the synthesis and catabolism of sugar phosphate in the former two.

Journal Article↗

PubMed1972

Decrease of Glucose 6-Phosphate and 6-Phosphogluconate Dehydrogenase Activities in the Xylem of Populus gelrica on Budding.

The activities of glucose 6-phosphate and 6-phosphogluconate dehydrogenases, transketolase, phosphoglucose isomerase, and fructose 6-phosphate kinase were studied in extracts of wintering poplar (Populus gelrica) xylem. The xylem of wintering poplar showed high levels of transketolase, glucose 6-phosphate, and 6-phosphogluconate dehydrogenases. On recommencement of growth, the two dehydrogenase activities decreased. The three remaining enzymes appeared to be unchanged. In spring and early summer, glucose 6-phosphate dehydrogenase of the xylem was extremely low. On the other hand, 6-phosphogluconate dehydrogenase, which also became lower during the metabolic shift from winter to spring, was readily detected, and was several times higher than glucose 6-phosphate dehydrogenase throughout the year. The low dehydrogenase activities lasted into late October and then appeared to resume their original activity. A shift of metabolism at the beginning of growth was also observed by measuring the amount of sugar phosphates, soluble amino acids and amides, and proteins in the xylem. In contrast to the decrease of the two dehydrogenases and soluble proteins at the time of budding, incorporation of lysine-U-(14)C into the xylem protein ramained constant. A method to transfuse radioactive compounds into a section of stem was described.

Journal Article↗