醤油麹菌Aspergillus sojaeのアルカリプロテアーゼ酵素蛋白質に結合するカルシウムの存在と酵素の安定性

概要

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(1) The thermo-stability of Aspergillus sojae alkaline proteinase increased by calcium ion and decreased by EDTA. Each effect on the thermo-stability was lost by eliminating calcium ion or EDTA by dialysis. (2) The proteinase preparation after dialysis against distilled water contained 1 gram atom of calcium per mole of enzyme protein and insignificant amounts of the other metal ions. Same result was obtained with the enzyme preparation after extensive dialysis against EDTA at low temperature. (3) EDTA promoted the inactivation of the enzyme at 50°C. There was a paral-lelism between the loss in activity and the increase in the rate of autodigestion. (4) The stabilities of the activity and the conformation of the enzyme at low pH region increased by calcium ion and decreased by EDTA. The loss of the enzyme activity by EDTA at low pH region was found to be irreversible. The role and the properties of the calcium atom, which seems to be tightly bound to the enzyme protein, are discussed.
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