Secondary structures of an enzyme (Candida cylindracea) in supercritical carbon dioxide and interactions operating between carbon dioxide and enzyme molecules were studied by Fourier transform infrared spectroscopy combined with microgravimetry at pressures of 6.86-19.12 MPa and at 304.1 K. It was found that, in very limited pressure range near the critical point of carbon dioxide, the interactions are greatly increased and allowed to provoke drastic conformational changes of the enzyme, causing active sites to emerge and catalyze the stereoselective synthesis of (S)-(-)-oleic acid 3,7-dimethyl-6-octenyl ester from oleic acid, and (+/-)-citronellol. Supercritical carbon dioxide medium in the near-critical region should be a trigger to the activation of the enzyme by causing the movement of surface groups and creating an active site, producing a stereoselective machinery.