title: Cyclitols protect glutamine synthetase and malate dehydrogenase against heat induced deactivation and thermal denaturation.
abstract: The accumulation of cyclitols in plants is a widespread response that provides protection against various environmental stresses. The capacity of myo-Inositol, pinitol, quercitol, and other compatible solutes (i.e., sorbitol, proline, and glycinebetaine) to protect proteins against thermally induced denaturation and deactivation was examined. Enzymatic activity measurements of L-glutamine synthetase from Escherichia coli and Hordeum vulgare showed that the presence of cyclitols during heat treatment resulted in a significantly higher percentage of residual activity. CD spectroscopy experiments were used to study thermal stabilities of protein secondary structures upon the addition of myo-Inositol, pinitol, and glucose. 0.4 M myo-Inositol was observed to raise the melting temperature (Tm) of GS from E. coli by 3.9 degrees C and MDH from pig heart by 3.4 degrees C, respectively. Pinitol showed an increase in Tm of MDH by 3.8 degrees C, whereas glucose was not effective. Our results show a great potential of stabilizing proteins by the addition of cyclitols.
authors.affiliation: Department of Biomolecular Structural Chemistry, University of Vienna, A-1030 Vienna, Austria. martina.jaindl@univie.ac.at
authors.forename: Martina
authors.initials: M
authors.lastname: Jaindl
authors.forename: Marianne
authors.initials: M
authors.lastname: Popp
mesh_terms: D002942:Circular Dichroism; D004795:Enzyme Stability / Q000187:drug effects*; D004926:Escherichia coli / Q000201:enzymology; D005947:Glucose / Q000494:pharmacology; D005974:Glutamate-Ammonia Ligase / Q000502:physiology*; D049670:History, 17th Century; D001467:Hordeum / Q000201:enzymology; D006358:Hot Temperature; D007294:Inositol / Q000031:analogs & derivatives / Q000494:pharmacology; D008291:Malate Dehydrogenase / Q000502:physiology*; D011489:Protein Denaturation / Q000187:drug effects*; D013402:Sugar Alcohols / Q000494:pharmacology*; D013816:Thermodynamics
chemical_list: D013402:Sugar Alcohols; C021730:pinitol; D007294:Inositol; D008291:Malate Dehydrogenase; D005974:Glutamate-Ammonia Ligase; D005947:Glucose