It has been long assumed that the x-ray crystal structure of an enzyme reveals the same conformation that occurs at the physiological temperature. Bovine carbonic anhydrase (BCA), an enzyme that consists of 259 amino acid residues, belongs to a class of enzymes called metalloenzymes which is due to the presence of a zinc-containing active site.  The function of BCA is to help regulate pH, fluid balance, and help transport CO2 out of tissues by catalyzing the hydration of CO2 to bicarbonate and protons.  Using slow-scan-rate differential scanning calorimetry, which employs scan rates as low as 0.010 K min-1 , we have revealed a conformational change that occurs around 30�C, a temperature between where the crystal structure was first determined  (4�C) and the bovine normal body temperature of 38.3 �C.  This suggests the physiological structure of BCA may differ from the x-ray structure.  Using standard methods we have calculated the thermodynamics of the low-to physiological-temperature conformational change.

Slow-scan-rate differential scanning calorimetry of bovine carbonic anhydrase

245th National Meeting (2013)

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