This title appears in the Scientific Report : 2011 

Structural stability of soybean (Glycine max) a-amylase: Properties of the unfolding transition studied with fluorescence and CD spectroscopy
Kumari, A.
Rosenkranz, T. / Kayastha, A.M. / Fitter, J.
Molekulare Biophysik; ICS-5
Protein and peptide letters, 18 (2011) S. 253 - 260
Schiphol Bentham Science Publ. 2011
253 - 260
10.2174/092986611794578305
Journal Article
BioSoft: Makromolekulare Systeme und biologische Informationsverarbeitung
Protein and Peptide Letters 18
J
Please use the identifier: http://dx.doi.org/10.2174/092986611794578305 in citations.
Stability and unfolding of mammalian and microbial alpha-amylases have been intensively investigated. However, there is only limited information available on the structural stability of plant alpha-amylases, namely of the two isoenzymes from barley AMY1 and AMY2, of the alpha-amylase from mung bean (Vigna radiata), and of the alpha-amylase from malted sorghum (Sorghum bicolor). We report here the stability of soybean alpha-amylase (GMA), against elevated temperatures and chemical denaturants (GndHCl) by employing circular dichroism and fluorescence spectroscopy. Since it is well-known that calcium ions play a crucial role for enzymatic activity and stability of alpha-amylases, we performed our studies with calcium bound and calcium free GMA. The thermal unfolding transition temperature decreased from 72 degrees C for calcium saturated samples to 57 degrees C for the case of calcium depleted GMA. Similarly, the GndHCl transition concentration was lowered from 0.70 M for calcium bound GMA to 0.41 M in the absence of calcium. Thermal unfolding of GMA is irreversible due to aggregation of the unfolded state. GMA unfolded in 6 M GndHCl shows high degree of reversibility after diluting the unfolded enzyme in native buffer containing 7 M glycerol. Furthermore, the refolded enzyme showed 93% of activity.