Energy charge control of the Calvin cycle enzyme 3-phosphoglyceric acid kinase

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Pea (Pisum sativum) leaf chloroplastic and cytoplasmic 3-phosphoglycerate kinases (ATP: D-3-phosphoglycerate 1-phosphotransferase, EC 2.7.2.3) have similar Michaelis constants for ATP, 0.7 and 0.55 mM, for ADP, 0.18 and 0.22, and for 3-P-glycerate, 0.59 and 0.54 mM at low substrate concentrations, and 1.6 and 1.25 mM at high substrate concentrations. Both enzymes are inhibited by ADP and AMP in the ATP-utilizing direction and by ATP and AMP in the ATPgenerating direction and are controlled by energy charge. Apparently, whether the cytoplasmic and chloroplastic kinases in the plant cell will participate in the reductive pentose phosphate cycle and gluconeogenesis or in glycolysis will be determined by the environment in the cell compartment and not by the differential properties of the enzymes themselves.3-Phosphoglycerate kinase (ATP: D-3-phosphoglycerate 1-phosphotransferase, EC 2.7.2.3) catalyzes the reversible interconversion of 3-P-glycerate and 1,3-diP-glycerate with the concomitant utilization or generation of ATP. This enzyme participates in the reductive pentose phosphate cycle and in glycolysis and gluconeogenesis in green plants. Although the chloroplastic and cytoplasmic forms of the enzyme have been separated by isoelectric focusing (4), further characterization of the two forms has been lacking. The purpose of the experiments described here was to determine and compare the properties of the two forms of 3-P-glycerate kinase.The pea (Pisum sativum L.) chloroplastic and cytoplasmic 3-P-glycerate kinases have identical pH optima, with Pglycerate as substrate, and similar or identical Michaelis constants for ATP, ADP, and 3-P-glycerate. Both forms are inhibited by AMP and ADP and the Ki values differ by a factor of 1.5. The only naturally occurring nucleoside triphosphate which serves as a phosphate donor is ATP. The pea leaf 3-P-glycerate kinases are apparently very similar enzymes and also resemble in many, but not all, respects the enzymes from pea seeds (8), yeast (13)(14)(15), rabbit muscle (13), and the chemosynthetic bacterium Hydrogenomonas facilis (19).

Section: Discussionmentioning

confidence: 99%

Chloroplast and Cytoplasmic Enzymes

Pacold¹,

Anderson²

1975

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“…Sellami (26), for example, reported a drop of 0.20 in the energy charge in the chloroplasts of wheat leaves on transferring the plants from light to dark, whereas the cytoplasmic energy charge remained higher (above 0.75) in the dark. Changes in the energy charge could conceivably be of great importance in plants in regulating the activities of energy-yielding and energy-utilizing pathways under different environmental conditions as suggested by Pacold and Anderson (22). Although the isoprenoid biosynthetic system found to be subject to energy charge regulation in the present work is derived from endosperm tissue devoid of chloroplasts, the results suggest the possibility that similar regulatory influences may be of importance to other isoprenoid biosynthetic activities in the plant including those present in the chloroplast.…”

Section: Discussionmentioning

confidence: 99%

“…Pacold and Anderson (22,23) have developed a case for energy charge regulation of the chloroplastidic and cytoplasmic 3-P-glycerate kinases in pea leaves which determined their ability to function in either the biosynthetic or glycolytic direction under different circumstances. Typical responses to energy charge expected for enzymes participating in biosynthetic sequences were seen for pea leaf glutamine synthetase by O'Neal and Joy (21) and for the argininosuccinate synthetase in soybean cells by Shargool (27).…”

Section: Discussionmentioning

confidence: 99%

Regulation of the Biosynthesis of Ent-Kaurene from Mevalonate in the Endosperm of Immature Marah macrocarpus Seeds by Adenylate Energy Charge

Knotz¹,

Coolbaugh²,

West³

1977

Thus, the energy charge is a measure of the extent to which the total pool of 5'-adenylates is present in the form of components containing phosphoanhydride bonds. It has been demonstrated that regulatory enzymes in many biosynthetic (energy-utilizing) sequences show a sharp increase in rate as the energy charge is increased through the physiologically important range of about 0.80 to 0.95 (2). Although this has been shown to be the case for many animal and microbial systems which have been studied, relatively little is known about adenylate energy charge regulation of higher plant systems.The results presented in this paper indicate that the rate of biosynthesis of kaurene from mevalonate in M. macrocarpus endosperm shows a response to variation in energy charge which is typical of a biosynthetic sequence. The rate-determining step in the sequence subject to this regulation appears to be the reaction catalyzed by pyrophosphomevalonate decarboxylase (EC 4.1.1.33) (step 3, Fig. 1). EXPERIMENTAL PROCEDUREMaterials. Immature seeds of M. macrocarpus (wild cucumber) were collected in the Santa Monica Mountains, California, during the spring of 1975 and frozen at -20 C for approximately 1 year before use. Pooled endosperm (100 ml) was then gently disrupted in a Thomas Teflon to glass homogenizer and centrifuged for 10 min at 10,000g to remove cell debris and larger particulate matter. The supematant fraction was further centrifuged at 150,000g for 90 min to remove particulate enzymes which catalyze the oxidative metabolism of kaurene and much of the phosphatase activity. This supernatant solution was then dialyzed against four 1-liter volumes of tris chloride (0.05 M, pH 7) in a rotating rapid-dialyzer over a period of 2 hr. The dialyzed preparation (55 ml, 1.7 mg protein/ml) served as the source of enzymes for all of the experiments reported. All enzyme preparation procedures were done at 0 to 4 C, and the enzyme solution was stored frozen in a liquid N2 refrigerator until ready for use.[2-"4C]MVA lactone (10.9 mCi/mmol) was purchased from

“…The flow rate of the air passing through the chamber was kept at 1.5 I/min. The measurement was performed until a steady-rate of CO2 exchange was obtained, and the rate at 300 Ml/l CO2 was corrected using the calibration equation reported by Kahn and Tsunoda (15 (23), respectively, with minor modifications. Both enzymes were assayed after activation of the enzyme preparations by incubating with 5 mm DTT.…”

mentioning

confidence: 99%

Photosynthesis and Ribulose 1,5-Bisphosphate Carboxylase in Rice Leaves

Makino¹,

Mae²,

Ohira³

1983

195

Changes in photosynthesis and the ribulose 1,5-bisphosphate (RuBP) carboxylase level were examined in the 12th leaf blades of rice (Oryza sativa L.) grown under different N levels. Photosynthesis was determined using an open infrared gas analysis system. The level of RuBP carboxylase was measured by rocket immunoelectrophoresis. These changes were followed with respect to changes in the activities of RuBP carboxylase, ribulose 5-phosphate kinase, NADP-glyceraldehyde 3-phosphate dehydrogenase, and 3-phosphoglyceric acid kinase.RuBP carboxylase activity was highly correlated with the net rate of photosynthesis (r = 0.968). Although high correlations between the activities of other enzymes and photosynthesis were also found, the activity per leaf of RuBP carboxylase was much lower than those of other enzymes throughout the leaf life. The specific activity of RuBP carboxylase on a milligram of the enzyme protein basis remained fairly constant (1.16 ± 0.07 micromoles of CO2 per minute per milligram at 25°C) throughout the experimental period.Kinetic parameters related to CO2 fixation were examined using the purified carboxylase. The Leaf photosynthesis shows large fluctuations with leaf age. As the leafgrows and chloroplasts are assembled, the photosynthetic activity rapidly increases to a maximum rate just after full expansion. Thereafter, the leaf steadily loses its photosynthetic capacity during senescence. Changes in the activities of stromal enzymes or electron transport in relation to photosynthesis have been studied during leaf senescence in various higher plants (4-6, 11, 27 The purpose of this study was to clarify whether RuBP carboxylase can be a factor that limits photosynthesis in a leaf during its life span. Using the 12th leaf blades on the main stems of rice, we studied changes in photosynthesis and RuBP carboxylase, and their responses to N supply. These changes were also followed in relation to changes in the activities of several other stromal enzymes (Ru5P kinase, NADP-G3P dehydrogenase, and PGA kinase). In vitro RuBP carboxylase activity, calculated at atmospheric CO2 level from its kinetic parameters, was comparable to the in situ true photosynthetic rate during the life span of the leaf. MATERIALS AND METHODS