Cyclitols protect glutamine synthetase and malate dehydrogenase against heat induced deactivation and thermal denaturation

• Published in: Biochemical and biophysical research communications Vol. 345; no. 2; pp. 761 - 765
• Main Authors: Jaindl, Martina, Popp, Marianne
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 30.06.2006
• Subjects: Circular Dichroism; Compatible solutes; Cyclitols; Enzyme Stability - drug effects; Escherichia coli; Escherichia coli - enzymology; Glucose - pharmacology; Glutamate-Ammonia Ligase - physiology; History, 17th Century; Hordeum - enzymology; Hordeum vulgare; Hot Temperature; Inositol - analogs & derivatives; Inositol - pharmacology; l-Glutamine synthetase; l-Malate dehydrogenase; Malate Dehydrogenase - physiology; myo-Inositol; Pinitol; Protein Denaturation - drug effects; Sugar Alcohols - pharmacology; Thermal stability; Thermodynamics; Compatible solutes; Pinitol; Cyclitols; myo-Inositol; l-Malate dehydrogenase; l-Glutamine synthetase; Thermal stability
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2006.04.144

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 ( T m) of GS from E. coli by 3.9 °C and MDH from pig heart by 3.4 °C, respectively. Pinitol showed an increase in T m of MDH by 3.8 °C, whereas glucose was not effective. Our results show a great potential of stabilizing proteins by the addition of cyclitols.