d-Mannitol dehydrogenase and d-mannitol-1-phosphate dehydrogenase in Platymonas subcordiformis: some characteristics and their role in osmotic adaptation

Richter, Dietmar; Kirst, G. O.

doi:10.1007/bf00402987

Cited by 43 publications

(20 citation statements)

References 27 publications

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“…2-4). Although the activation of M1PDH by NaCl has been reported for the prasinophyte P. subcordiformis (Richter and Kirst, 1987), no report has been found about its effect on K m (F6P) or the optimum pH value. Sulfate was found to be more effective than chloride for the activation of M1PDH in C. continua (Fig.…”

Section: Discussionmentioning

confidence: 98%

“…The characterization of algal M1PDH has only previously been performed with crude or partially purified preparations from the prasinophycean alga Platymonas subcordiformis (Richter and Kirst, 1987), the brown alga Spatoglossum pacificum (Ikawa et al, 1972), and the red alga C. leprieurii (Karsten et al, 1997a(Karsten et al, , 1997b; Table III). Effective and complete purification was possible by introducing the PEG/AS treatment and affinity chromatography with Reactive Red 120 agarose.…”

Section: Discussionmentioning

confidence: 99%

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Characterization of Salt-Regulated Mannitol-1-Phosphate Dehydrogenase in the Red Alga Caloglossa continua

2003

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Mannitol-1-phosphate (M1P) dehydrogenase (M1PDH; EC 1.1.1.17), an enzyme catalyzing the reduction of Fru-6-phosphate (F6P) to M1P in algal mannitol biosynthesis, was purified to homogeneity from a cell homogenate of the eulittoral red alga Caloglossa continua (Okamura) King et Puttock. The enzyme was a monomer with an apparent molecular mass of 53 kD, as determined by gel filtration and SDS-PAGE, and exhibited an pI of approximately 5.5. The substrate specificity was very high toward F6P and M1P for respective reductive and oxidative reactions. The enzyme was found to be a sulfhydryl-type, because its activity was inhibited by N-ethylmaleimide and p-hydroxymercuribenzoate, and the inhibition by p-hydroxymercuribenzoate was rescued by 2-mercaptoethanol. Some unknown factors in the extract may also have inhibited the activity, because the total activity was greatly increased through the purification procedure. The optimum pH for F6P reduction was changed from 6.0 or lower to 7.2 by the addition of 200 mm NaCl. The reduction of F6P showed strong substrate inhibition above 0.5 mm. However, K m (F6P) of M1PDH was increased eight times by the addition of 200 mm NaCl, whereas V max was in a similar range with the avoidance of substrate inhibition by F6P. These results indicate that the enzyme was finely and directly regulated by the salt concentration without the requirement for gene expression. M1PDH can therefore be a key enzyme for regulating mannitol biosynthesis when the alga is stressed by a salinity change.

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Characterization of Salt-Regulated Mannitol-1-Phosphate Dehydrogenase in the Red Alga Caloglossa continua

2003

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“…In Dunaliella, increases in glycerol synthesis are associated with salt stimulation of a key biosynthetic enzyme, a chloroplastic dihydroxyacetone phosphate reductase (Goyal et al, 1987;Gee et al, 1993). In the marine alga Platymonas subcordiformis, osmotic-induced changes in mannitol levels have been associated with differential salt effects on the synthetic and degradative enzymes (Richter and Kirst, 1987). We have not studied salt effects on M6PR in detail, but provisional data suggest that salt inhibits in vitro activity (W.H.…”

Section: Discussionmentioning

confidence: 99%

Gas Exchange and Carbon Partitioning in the Leaves of Celery (Apium graveolens L.) at Various Levels of Root Zone Salinity

et al. 1994

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Both mannitol and sucrose (Suc) are primary photosynthetic products in celery (Apium graveolens 1.). In other biological systems mannitol has been shown to serve as a compatible solute or osmoprotectant involved in stress tolerance. Although mannitol, like SUC, is translocated and serves as a reserve carbohydrate in celery, its role in stress tolerance has yet to be resolved. Mature celery plants exposed to low (25 mM NaCI), intermediate (100 mM NaCI), and high (300 mM NaCI) salinities displayed substantial salt tolerance. Shoot fresh weight was increased at low NaCl concentrations when compared with controls, and growth continued, although at slower rates, even after prolonged exposure to high salinities. Gas-exchange analyses showed that low NaCl levels had little or no effect on photosynthetic carbon assimilation (A), but at intermediate levels decreases in stomatal conductance limited A, and at the highest NaCl levels carboxylation capacity (as measured by analyses of the CO, assimilation response to changing internal CO, partial pressures) and electron transport (as indicated by fluorescence measurements) were the apparent prevailing limits to A. Increasing salinities up to 300 mM, however, increased mannitol accumulation and decreased SUC and starch pools in leaf tissues, e.g. the ratio of mannitol to SUC increased almost 10-fold. These changes were due in part to shifts in photosynthetic carbon partitioning (as measured by "C labeling) from SUC into mannitol. Salt treatments increased the activity of mannose-6-phosphate reductase (MCPR), a key enzyme in mannitol biosynthesis, 6-fold in young leaves and 2-fold in fully expanded, mature leaves, but increases in MCPR protein were not apparent in the older leaves. Mannitol biosynthetic capacity (as measured by labeling rates) was maintained despite salt treatment, and relative partitioning into mannitol consequently increased despite decreased photosynthetic capacity. The results support a suggested role for mannitol accumulation in adaptation to and tolerance of salinity stress.The polyols were the first class of compounds to be termed compatible solutes (Brown and Simpson, 1972), and many of these compounds (acyclic polyols, e.g. sorbitol, mannitol, and glycerol, and substituted cyclic polyols, e.g. pinitol) and several related derivatives (e.g. glycerol glucoside) play roles in stress protection in almost all classes of living organisms,

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“…the simultaneous occurrence of all four enzymes) has been demonstrated only for fungi (Hult & Gatenbeck, 1979) and parasitic protozoans (Schmatz, 1989), the florideophycean red alga Caloglossa leprieurii (Karsten et al, 1997) and now the rhodellophycean alga Dixoniella grisea (Tables 3-6). Richter & Kirst (1987) established the occurrence of only Mt1PDH/MtDH in the unicellular green alga Tetraselmis subcordiformis (as Platymonas subcordiformis). Furthermore, even though mannitol is the main photosynthetic product of brown algae (Reed et al, 1985), the simultaneous occurrence of only Mt1PDH/Mt1Pase has been proven for this algal group (Ikawa et al, 1972).…”

Section: Discussionmentioning

confidence: 99%

“…The mannitol pool is also controlled by abiotic factors, in particular pH and salinity (Richter & Kirst, 1987;Karsten et al, 1997;Iwamoto et al, 2003;Tables 3-6). In Dixoniella grisea, pH had little influence on most enzymes.…”

Section: Discussionmentioning

confidence: 99%

Biochemical characterization of mannitol metabolism in the unicellular red algaDixoniella grisea(Rhodellophyceae)

Eggert

Raimund

Daele

et al. 2006

European Journal of Phycology

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The mannitol cycle has been verified in a unicellular red alga (Rhodellophyceae) for the first time. All four enzymes involved in the cycle (mannitol-1-phosphate dehydrogenase, Mt1PDH: EC 1.1.1.17; mannitol-1-phosphatase, Mt1Pase: EC 3.1.3.22; mannitol dehydrogenase, MtDH: 1.1.1.67; hexokinase, HK: 2.7.1.1.) were detected and characterized in crude algal extracts from Dixoniella grisea. These enzymes, with the exception of Mt1Pase, were specific to their corresponding substrates and nucleotides. The activities of enzymes in the anabolic pathway (fructose-6-P reduction by Mt1PDH and mannitol-6-P reduction by Mt1Pase) were at least 2-to 4-fold greater than those of the catabolic pathway (mannitol oxidation by MtDH and fructose oxidation by HK). There appears to be, therefore, a net carbon flow in D. grisea towards a high intracellular mannitol pool. The mannitol cycle guarantees a rapid accumulation or degradation of mannitol within algal cells in response to changing salinity in natural habitats. Moreover, the demonstration of the mannitol cycle within the Rhodellophyceae provides evidence that this metabolic pathway is of ancient origin in the red algal lineage.

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d-Mannitol dehydrogenase and d-mannitol-1-phosphate dehydrogenase in Platymonas subcordiformis: some characteristics and their role in osmotic adaptation

Cited by 43 publications

References 27 publications

Characterization of Salt-Regulated Mannitol-1-Phosphate Dehydrogenase in the Red Alga Caloglossa continua

Characterization of Salt-Regulated Mannitol-1-Phosphate Dehydrogenase in the Red Alga Caloglossa continua

Gas Exchange and Carbon Partitioning in the Leaves of Celery (Apium graveolens L.) at Various Levels of Root Zone Salinity

Biochemical characterization of mannitol metabolism in the unicellular red algaDixoniella grisea(Rhodellophyceae)

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