Characterization of mannitol metabolism in the mangrove red algaCaloglossa leprieurii (Montagne) J.Agardh

Karsten, Ulf; Barrow, Kevin D.; Nixdorf, Oliver; West, John A.; King, Robert

doi:10.1007/bf01007701

Cited by 41 publications

(29 citation statements)

References 27 publications

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“…The wider substrate specificity previously reported (e.g. Karsten et al, 1997a) might possibly have been due to contaminants, because the assay was performed with crude extracts. The inhibition by such sulfhydryl reagents as pHMB and NEM indicates that M1PDH can be considered as an SH enzyme (see Table III).…”

Section: Discussionmentioning

confidence: 93%

“…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%

“…Because M1PDH in C. continua was found to be an acidic protein with low pI (approximately 5.5), a similar mechanism for stabilization might also be expected in this enzyme. On the other hand, when the salt stress is released, the concentration of Cl Ϫ in vivo can be expected to decrease (Mostaert et al, 1995b), and that of F6P would be increased by the mannitol-catabolizing pathway with mannitol dehydrogenase and hexokinase (Karsten et al, 1997a(Karsten et al, , 1997b. Under these conditions the F6P-reducing activity would be limited, and carbon flow toward mannitol biosynthesis might be reduced.…”

Section: Discussionmentioning

confidence: 99%

“…4). Because M1PDH is a cytoplasmic enzyme (Karsten et al, 1997a), the enzyme will be activated in vivo by such a pH change. As for the kinetic parameters, Figure 3A and Table II indicate that the activity for F6P reduction in the absence of NaCl was a maximum at 0.5 mm F6P and was strongly inhibited by the substrate above this concentration.…”

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: 93%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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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“…While energetically expensive, plants may permanently keep these adaptive mechanisms in place in anticipation of inevitable changes in environmental conditions. A mannitol cycle involving fructose, fructose-6-phosphate and mannitol-1-phosphate was recently identified in a eulittoral mangrove red alga and proposed to function in biochemical adaptation to fluctuating environmental extremes in this habitat (Karsten et al 1997). Constitutive acclimatory mechanisms are likely to be of particular value in amelioration of stress damage in the short term, although amplification of their efficacy through subsequent modulation of gene expression may prevent damage arising from long-term exposure to adverse conditions.…”

Section: The Roles Of Osmolyte Accumulation During Stress 545mentioning

confidence: 99%

Dissecting the roles of osmolyte accumulation during stress

Hare

Cress

Staden

1998

Plant Cell & Environment

1,197

744

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Many plants accumulate organic osmolytes in response to the imposition of environmental stresses that cause cellular dehydration. Although an adaptive role for these compounds in mediating osmotic adjustment and protecting subcellular structure has become a central dogma in stress physiology, the evidence in favour of this hypothesis is largely correlative. Transgenic plants engineered to accumulate proline, mannitol, fructans, trehalose, glycine betaine or ononitol exhibit marginal improvements in salt and/or drought tolerance. While these studies do not dismiss causative relationships between osmolyte levels and stress tolerance, the absolute osmolyte concentrations in these plants are unlikely to mediate osmotic adjustment. Metabolic benefits of osmolyte accumulation may augment the classically accepted roles of these compounds. In re-assessing the functional significance of compatible solute accumulation, it is suggested that proline and glycine betaine synthesis may buffer cellular redox potential. Disturbances in hexose sensing in transgenic plants engineered to produce trehalose, fructans or mannitol may be an important contributory factor to the stress-tolerant phenotypes observed. Associated effects on photoassimilate allocation between root and shoot tissues may also be involved. Whether or not osmolyte transport between subcellular compartments or different organs represents a bottleneck that limits stress tolerance at the whole-plant level is presently unclear. None the less, if osmolyte metabolism impinges on hexose or redox signalling, then it may be important in long-range signal transmission throughout the plant.Key-words: betaine; cold stress; drought; fructans; mannitol; osmolytes; proline; salinity; sugar signalling; trehalose. Abbreviations INTRODUCTIONEnvironmental stress is the major factor limiting plant productivity . Abiotic stresses which cause depletion of cellular water (drought, high soil salinity and temperature extremes) are responsible for the greatest agricultural losses. Upon exposure to these prevalent stresses, many plants accumulate organic osmolytes, most commonly polyhydroxylic compounds (saccharides and polyhydric alcohols) and zwitterionic alkylamines (amino acids and quaternary ammonium compounds).Several recent reviews discuss osmolyte accumulation in plants (Ingram & Bartels 1996;Serrano 1996). It is generally accepted that the increase in cellular osmolarity which results from the accumulation of non-toxic (thus 'compatible') osmotically active solutes is accompanied by the influx of water into, or at least a reduced efflux from, cells, thus providing the turgor necessary for cell expansion. None the less, a conclusive demonstration that osmotic adjustment contributes to fitness in stressful environments has yet to be achieved (Munns 1993). Since all subcellular structures must exist in an aqueous environment, tolerance to dehydration also depends on the ability of cells to maintain membrane integrity and prevent protein denaturation. Hypotheses that attribut...

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Mangroves

Lüttge¹

Salinity: Environment - Plants - Molecules

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Characterization of mannitol metabolism in the mangrove red algaCaloglossa leprieurii (Montagne) J.Agardh

Cited by 41 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

Dissecting the roles of osmolyte accumulation during stress

Mangroves

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