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NITROGEN METABOLISM OF HALOPHYTES.
Author(s) -
AHMAD I.,
LARHER F.,
MANN A. F.,
McNALLY S. F.,
STEWART G. R.
Publication year - 1982
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1982.tb03337.x
Subject(s) - halophyte , glutamine synthetase , betaine , glutamate synthase , proline , enzyme , chemistry , botany , biochemistry , ammonium , biology , glutamine , amino acid , salinity , organic chemistry , ecology
S ummary Ion‐exchange chromatography on DEAE‐Sephacel revealed the presence of two forms of glutamine synthestase (GS I and GS II ) in leaf tissue and one form in root tissue of the angiosperm halophyte, Triglochin maritima . The chromatographic characteristics of GS I and the root enzyme were similar but there were differences in their stability, GS I being considerably more stable than the root enzyme. The characteristics of GS I and GS II exhibited some differences, GS II showed negative cooperativity with respect to glutamate and had a pH optimum of 8 − 0 compared with 7.2 for GS I . GS I was found to be unstable, particularly in the presence of inorganic salts. Compounds such as glycine betaine, proline and sorbitol, which are thought to function as compatible osmotic solutes in halophytes, were found to stabilize GS II .