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Veränderung der aktivität der phosphoenolpyruvat-carboxylase durch NaCl bei halophyten verschiedener biotope

1974; Elsevier BV; Volume: 71; Issue: 5 Linguagem: Inglês

10.1016/s0044-328x(74)80101-7

0044-328X

Siegfried Treichel, Gunter O. Kirst, D. J. von Willert,

Enzyme function and inhibition

This paper reports effects of NaCl on in vitro activity of PEP carboxylase as well as on specific activity of the same enzyme isolated from various halophytes grown under saline and non-saline conditions. The objects investigated were the halophytes Aster tripolium, Plantago maritima, Honckenya peploides, Salicornia fruticosa, Carpobrotus edulis, Mesembryanthemum crystallinum, and Mesembryanthemum nodiflorum. While the halophytes Salicornia and Plantago show no change in specific activity of PEP carboxylase depending on salination, the halophytes Carpobrotus and Mesembryanthemum exhibit drastic responses under the same conditions. 200 mM NaCl growing solution causes a 3-fold and 3.6-fold increase in specific activity in Mesembryanthemum nodiflorum and Carpobrotus edulis,, respectively. Mesembryanthemum crystallinum exhibits a 5.5-fold increase when treated with 300 mM NaCl, and Carpobrotus edulis shows a 8.3-fold increase in 400 mM NaCl growing solution. A double reciprocal plot shows a noncompetitive interaction between the source of the enzyme and PEP indicating that the ratio PEP carboxylase to total extractable protein is altered by NaCl (Carpobrotus edulis and Mesembryanthemum crystallinum). This is not the case in Plantago and Salicornia where the values for Vmax are unaffected. Mesembryanthemum nodiflorum shows an uncompetitive interaction. The effect of NaCl on in vitro activity of PEP carboxylase does not depend on the source of enzyme. Enzyme preparations of all investigated plants show a marked inhibition following the addition of NaCl to the assay. The magnitude of this inhibition is not correlated with salt tolerance. Furthermore, enzymes isolated from plants grown in salinity react more sensitive than those enzymes isolated from plants grown in the absence of NaCl. A double reciprocal plot shows a competitive interaction between NaCl and PEP. Our results suggest a correlation between the response of PEP carboxylase to NaCl and plant habitat in the way that halophytes of the foreshore dunes exhibit a drastic increase in specific activity of this enzyme due to salinity not found in salt marsh halophytes.