Premium
Effects of stabilizing solutes on salt activation of phosphoenolpyruvate carboxylase from various plant sources
Author(s) -
ShooterIlan Adiva,
Waisel Yoav
Publication year - 1986
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1986.tb05755.x
Subject(s) - phosphoenolpyruvate carboxylase , betaine , pyruvate carboxylase , halophyte , chemistry , proline , carbon fixation , enzyme assay , enzyme , substrate (aquarium) , glycerol , biochemistry , botany , photosynthesis , salinity , biology , amino acid , ecology
Phosphoenolpyruvate carboxylase (PEP carboxylase EC 4.1.1.31) was extracted from various halophytic, semi‐halophytic and glycophytic plant species. When the enzyme of those extracts was substrate protected, and in the presence of 1.6 m M PEP in the reaction mixture, the activity of PEP carboxylase was increased by 100 m M NaCl, and the activity range in the presence of NaCl was expanded. No correlation could be established between the response of the enzyme to ions and various plant characteristics, such as taxonomic status, salt tolerance or carbon fixation pathways. Salt activation of PEP carboxylase was substrate (PEP) dependent, but the minimal substrate concentration varied in different species. Effects of the stabilizing solutes PEP, betaine, proline and glycerol on the kinetic properties of PEP carboxylase from Zea mays (L.) cv. Hazera were analyzed. In the absence of NaCl the slope of the Hill plot (n It ) tended to rise in the presence of these solutes. Stabilization of the enzyme with betaine or glycerol caused a decrease in K′. while K′ and VTO increased in the presence of PEP. NaCl (100 mM) caused an increase in both K′ and V max in the protected as well as in the unprotected enzyme, except for PEP protection, where K′ decreased somewhat. In the presence of the protectants, glycerol and PEP, the effect of NaCl on V max , was 2–4 times higher than its effect on the non‐protected enzyme.