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Effect of pH on subunit association and heat protection of soybean alpha-galactosidaseSoybeans contain the enzyme alpha-galactosidase, which hydrolyzes alpha-1, 6 linkages in stachyose and raffinose to give sucrose and galactose. We have found that galactose, a competitive product inhibitor of alpha-galactosidase, strongly promotes the heat stability of the tetrameric form of the enzyme at pH 4.0 and at temperatures of up to 70 degrees C for 60 min. Stachyose and raffinose also protect alpha-galactosidase from denaturation at pH 4.0 although to a lesser extent. Glucose and mannose have little effect. At pH 7.0 the enzyme is a monomer, and galactose has no effect on the heat stability of the enzyme. In the absence of heat protection of the enzyme by added sugars, a series deactivation mechanism was found to describe the deactivation data. In comparison, a unimolecular, non-first order deactivation model applies at pH 4.0, where heat protection effects were observed. At a temperature above 60 degrees C, simple deactivation is a suitable model. The results suggest that alpha-galactosidase conformation and heat stability are directly related.
Document ID
20040089464
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Porter, J. E.
(Purdue University West Layfayette, Indiana, United States)
Sarikaya, A.
Herrmann, K. M.
Ladisch, M. R.
Mitchell, C. A.
Date Acquired
August 21, 2013
Publication Date
August 1, 1992
Publication Information
Publication: Enzyme and microbial technology
Volume: 14
ISSN: 0141-0229
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: BCS 8912150
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Plant Biology

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