A chemically modified α-amylase with a molten-globule state has entropically driven enhanced thermal stability

QC 20140826
The thermostability properties of TAA were investigated by chemically modifying carboxyl groups on the surface of the enzyme with AMEs. The TAAMOD exhibited a 200 improvement in starch-hydrolyzing productivity at 60°C. By studying the kinetic, thermodynamic and biophysical properties, we found that TAAMOD had formed a thermostable, MG state, in which the unfolding of the tertiary structure preceded that of the secondary structure by at least 20°C. The X-ray crystal structure of TAAMOD revealed no new permanent interactions (electrostatic or other) resulting from the modification. By deriving thermodynamic activation parameters of TAAMOD, we rationalised that thermostabilisation have been caused by a decrease in the entropy of the transition state, rather than being enthalpically driven. Far-UV CD shows that the origin of decreased entropy may have arisen from a higher helical content of TAAMOD. This study provides new insight into the intriguing properties of an MG state resulting from the chemical modification of TAA.

NATURVETENSKAP Biologi Biokemi och molekylärbiologi hsv//swe
NATURAL SCIENCES Biological Sciences Biochemistry and Molecular Biology hsv//eng
activation thermodynamics
calorimetry
entropy
enzyme kinetics
protein X-ray crystallographic structure

Poljak, A. (author)
De Francisci, D. (author)
Guerriero, GeaUniversity of New South Wales, Sydney, Australia(Swepub:kth)u1p3u22n (author)
Pilak, O. (author)
Burg, D. (author)
Raftery, M. J. (author)
Parkin, D. M. (author)
Trewhella, J. (author)
Cavicchioli, R. (author)
University of New South Wales, Sydney, Australia (creator_code:org_t)

In:Protein Engineering Design & Selection: Oxford University Press (OUP)23:10, s. 769-7801741-01261741-0134

By the author/editor: Siddiqui, K. S.; Poljak, A.; De Francisci, D.; Guerriero, Gea; Pilak, O.; Burg, D.; show more...; Raftery, M. J.; Parkin, D. M.; Trewhella, J.; Cavicchioli, R.; show less...

About the subject

NATURAL SCIENCES: NATURAL SCIENCES; and Biological Scien ...; and Biochemistry and ...

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