Journal
BIOPHYSICAL CHEMISTRY
Volume 137, Issue 2-3, Pages 88-94Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bpc.2008.07.004
Keywords
Yeast hexokinase B; Thermoinactivation; Aggregation; Deamidation; Size exclusion-HPLC
Funding
- University of Tehran
- Iranian National Science Foundation (INSF)
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Yeast hexokinase has been poorly characterized in regard with its stability. In the present study, various spectroscopic techniques were employed to investigate thermal stability of the monomeric form of yeast hexokinase B (YHB). The enzyme under-went a conformational transition with a T-m of about 41.9 degrees C. The structural transition proved to be significantly reversible below 55 degrees C and irreversible at higher temperatures. Thermoinactivation studies revealed that enzymatic activity diminished significantly at high temperatures, with greater loss of activity observed above 55 degrees C. Release of ammonia upon deamidation of YHB obeyed a similar temperature-dependence pattern. Dynamic light scattering and size exclusion-HPLC indicated formation of stable aggregates. Taking various findings on the influence of osmolytes and chaperone-like agents on YHB thermal denaturation together, it is proposed that the purely conformational transition of YHB is reversible, and irreversibility is due to aggregation, as a major cause. Deamidation of a critical Asn or Gin residue(s) may also play an important role. (C) 2008 Elsevier B.V. All rights reserved.
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