NADP-dependent Glyceraldehyde 3-phosphate Dehydrogenase Research Articles

Increase in chloroplastic thiol groups by SO2 and its effect on light modulation of NADP-dependent glyceraldehyde 3-phosphate dehydrogenase

In broken spinach chloroplasts the total amount of thiol groups is about 3.7 μmol mg(-1) chlorophyll. Two thirds are represented by the masked form (which is only titratable after unfolding of the protein). Of the free groups, those reacting with NBD·Cl (1.2-2.0 μmol mg(-1) chlorophyll) seem to be undergoing oxidation more readily than those reacting with DTNB (1.0 μmol mg(-1) chlorophyll). SO2 application causes a maximal increase of 25% in free thiols, and doubles the amount of the masked thiols. The light triggered increase in SH, which starts at an elevated level, runs parallel to that of the controls. SO2 application of 1.8 mg m(-3) (=28 nmol l(-1)) for 1 h does not affect the dark level of NADP-GPD but enhances the light modulation by increasing the ratio of activation. This enhancement is explained by an increase in masked thiol groups during the preceding fumigation period.

Benzyladenine accelerates chloroplast differentiation and stimulates photosynthetic enzyme activity in cucumber cotyledons

The chloroplasts of etiolated cucumber cotyledons had crystalline prolamellar bodies, whereas those treated with benzyladenine (BA) have a well-developed plastid membrane system. After 4 h of exposure to light, grana were formed in the chloroplasts of BA-treated cotyledons but not in the controls. The specific activities of ribulose 1,5-diphosphate carboxylase, and NADP-dependent glyceraldehyde 3-phosphate dehydrogenase increased 75 and 50% respectively during BA treatment in the dark, while there was little change in the controls. On exposure to light, enzyme activities increased in both control and BA-treated cotyledons. Inhibitors of protein synthesis eliminated the BA stimulation of ribulose diphosphate carboxylase but had little effect on the BA stimulation of NADP-dependent glyceraldehyde 3-phosphate dehydrogenase activity. This study indicates that BA stimulates structural differentiation of the chloroplast and enhances activities of photosynthetic enzymes, even in the dark.

Aktivitätsänderungen von Enzymen bei Chlorogonium elongatum unter dem einfluß von rotem und blauem licht

Summary The structure of the plastids as well as the content of chlorophyll become reduced, when the alga Chlorogonium elongatum is growing on acetate in the dark. Transferred to red or blue light these cells get their green color in 8–10 hours. During adaptation to autotrophic growth enzymes change their activity. Blue or red light have an unequal influence on this change. The activity of the NADP-dependent glyceraldehydephosphate dehydrogenase and phosphoenolpyruvate carboxylase are more enhanced in blue light, whereas the activity of isocitratase decreases to a greater extent than in red light. The intensities of the red and blue light were chosen to give an equal dry weight production during autotrophic growth. Cells grown in blue light had a higher nitrogen content and less carbohydrate than in red.

Die Regulation des Photosyntheseapparates bei Chlorogonium elongatum Dangeard unter dem Einfluß von Licht und Acetat

Chlorogonium elongatum D angeard , an acetate alga, is characterized by its high productivity. Its growth constants in both, autotrophic and heterotrophic cultures exceed those of common strains of Chlorella or Euglena by a factor of 3–4. This seems remarkable in view of the large size of the cells (16 × 9μm). In cultures transferred from autotrophic growth to dark growth on acetate the plastids maintain nearly their original size; their internal membranes, however, are reduced to some single thylakoids or vesicles. Correspondingly, chlorophyll and activity of carboxydismutase (RuDPCO) become reduced to 5 and 10 % of that of the autotrophic culture. NADP-dependent glyceraldehydephosphate dehydrogenase (GAPDH) cannot be detected in heterotrophic cells; NAD-dependent GAPDH could be found in slight amounts. While isocitratase activity increases to a nine-fold amount by acetate growth, phosphoenolpyruvate carboxylase at the same time is reduced to about 50 %. When the cells had consumed the acetate in the dark, chlorophyll as well as RuDPCO and NAD-GAPDH begin to increase. NADP‐GAPDH is formed within a very short time; its activity surpasses that of the NAD-enzyme by 300 % after 8 hours Starting from dark cells, complete autotrophy is attained in the light within 8 hours. In this case, both types of GAPDH are produced, the NAD type, however, to a smaller extent

Hohe Strahlenresistenz der Aktivit�t und der lichtinduzierten Aktivit�tssteigerung der NADP-abh�ngigen Glycerinaldehyd-3-Phosphat-Dehydrogenase in Ankistrodesmus braunii

In Ankistrodesmus braunii, a unicellular alga, the activity of NADP-dependent glyceraldehyde phosphate dehydrogenase (GPD) in darkness is very resistant to X-rays. The light-induced increase in the activity of this enzyme within one minute is also not affected by irradiation. Doses up to 1060 Krad had no inhibitory effect. The increase of GPD activity during the life cycle, however, is very sensitive to X-rays.

Characterization of cytokinin action on enzyme formation during the development of the photosynthetic apparatus in rye seedlings

The action of cytokinin on the formation of photosynthetic enzymes in rye seedlings, which was described earlier, is further characterized by studying the interactions of kinetin with specific inhibitors of protein synthesis and with auxins. The combined action of cytokinin and auxin simultaneously affects enzymes of the oxidative pentose phosphate cycle which show a definite relationship to the appearance of the photosynthetic apparatus. 1. The formation of the photosynthetic enzyme carboxydismutase (EC 4.1.1.39) in rye seedlings can be almost completely prevented by chloramphenicol, but is also strongly inhibited by cycloheximide. These effects of chloramphenicol and cycloheximide cannot be overcome by the application of kinetin. 2. Plastid growth as well as the formation of photosynthetic enzymes (carboxydismutase; NADP-dependent glyceraldehydephosphate dehydrogenase, EC 1.2.1.9) are selectively curtailed in dark- or light-grown rye seedlings by treatment with relatively high concentrations of auxins like 3-indoleacetic acid, α-naphthalene-acetic acid (NAA) or 2,4-dichlorophenoxyacetic acid. 3. The inhibition of plastid growth and enzyme formation can be overcome to an increasing extent by applying increasing amounts of kinetin to young seedlings simultaneously with the NAA. Conversely, the promoting effect of kinetin on the formation of photosynthetic enzymes can be lowered by simultaneous application of NAA. In older seedlings the effect of NAA is no longer reversed by kinetin. An interpretation of the particularly high cytokinin requirement for the synthesis of photosynthetic enzymes in the seedlings is proposed. The appearance of the photosynthetic enzymes in the dark and in the light is accompanied by a decline in the rate of accumulation of key enzymes of the oxidative pentose phosphate cycle, especially glucose-6-phosphate dehydrogenase (EC 1.1.1.49). This effect is not due to a simple insufficiency of nutrients. Moreover, applications of glucose-6-phosphate or 6-phosphogluconate did not suggest an inducing effect of these substrates on their corresponding enzymes. No further increase of glucose-6-phosphate dehydrogenase can be achieved by application of either kinetin or NAA alone. But the formation of this enzyme continues at a high rate and reaches nearly twice the maximal activity of the controls when high concentrations of kinetin and NAA are applied simultaneously. It is concluded that a specific effect of the auxin and the diminished competition of the plastids for the promoting effect of kinetin contribute to the increased formation of glucose-6-phosphate dehydrogenase.The role of cytokinins in the control of the described enzymes is discussed.

Influence of cytokinins on the formation of photosynthetic enzymes in rye seedlings

1. Factors were investigated which control the formation of photosynthetic enzymes during germination. Enzymes of the reductive pentose phosphate cycle like carboxydismutase (EC 4.1.1.39) and NADP-dependent glyceraldehydephosphate dehydrogenase (EC 1.2.1.9.) are formed in the primary leaves of dark-grown rye seedlings. The rate of their synthesis is determined by the level of cytokinins. This rate can be increased by treatment of normal seedlings with kinetin. After application of kinetin to dark-grown seedlings, the investigated enzymes finally reach the same activity as they do in untreated light-grown plants. The formation of these photosynthetic enzymes can be strongly reduced by excision of the roots early in the development, a treatment which is known to lower the supply of cytokinins. A high rate of enzyme formation can be restored by feeding kinetin to rootless seedlings. Neither adenosine nor gibberellic acid have this effect on enzyme formation. 2. Changes in the content of cytokinins preferentially influence the formation of the investigated photosynthetic enzymes. Some cytoplasmic enzymes are not affected by the decrease of the cytokinin level which is achieved by excision of the roots. At the beginning of germination only cytoplasmic enzymes are promoted by application of kinetin, whereas in later stages, after 96 hours of germination, only the formation of photosynthetic enzymes is increased. The formation of photosynthetic and cytoplasmic enzymes seem to differ in their cytokinin requirements. 3. Cytokinins seem to be necessary for the formation of enzymes of the reductive pentose phosphate cycle. However, the cytokinins do not alter the time of appearance of these enzymes. Also the suppressing action which is exerted on the formation of photosynthetic enzymes by low temperature cannot be prevented by the application of kinetin. The action of cytokinins probably does not induce the derepression of the genes, but the level of cytokinins determines the extent of the manifestation of the genes. 4. The formation of the photosynthetic enzymes is also promoted by phytochrome. Phytochrome and cytokinin act as independent factors in a multiplicative system. The rate of synthesis of these enzymes in the dark, which corresponds to the cytokinin level of the seedlings (rootless, normal or treated with kinetin) can be increased by a constant factor via the phytochrome system by continuous irradiation with far-red light. In the case of carboxydismutase this factor is nearly 2. 5. After excision of the roots carboxydismutase and NADP-dependent glyceraldehydephosphate dehydrogenase reach higher activity in red and blue light than in far-red light, under which no chlorophyll is formed. In this case formation of carboxydismutase in red and blue light seems to proceed in close correlation with chlorophyll synthesis.