TAILIEUCHUNG - Báo cáo khoa học: Sub-zero temperature inactivation of carboxypeptidase Y under high hydrostatic pressure

High hydrostatic pressure induced cold inactivation of carboxypeptidase Y. Carboxypeptidase Y was fully active when exposed to subzero temperature at MPa; however, the enzyme became inactive when high hydrostatic pressure and subzero temperature were both applied. When the enzyme was treated at pressures higher than 300 MPa and temperatures lower than)5 C, it underwent an irreversible inactivation in which nearly 50% of the a-helical structure was lost as judged by circular dichroism spectral analysis | Eur. J. Biochem. 269 4666-4674 2002 FEBS 2002 doi Sub-zero temperature inactivation of carboxypeptidase Y under high hydrostatic pressure Toshihiko Kinsho1 Hiroshi Ueno1 t Rikimaru Hayashi1 Chieko Hashizume2 and Kunio Kimura2 t 1 Division of Applied Life Sciences Graduate School of Agriculture Kyoto University Sakyo Japan 2Meidi-Ya Food Factory Co. Ibaraki Osaka Japan High hydrostatic pressure induced cold inactivation of carboxypeptidase Y. Carboxypeptidase Y was fully active when exposed to subzero temperature at MPa however the enzyme became inactive when high hydrostatic pressure and subzero temperature were both applied. When the enzyme was treated at pressures higher than 300 MPa and temperatures lower than -5 C it underwent an irreversible inactivation in which nearly 50 of the a-helical structure was lost as judged by circular dichroism spectral analysis. When the applied pressure was limited to below 200 MPa the cold inactivation process appeared to be reversible. In the presence of reducing agent this reversible phenomenon observed at below 200 MPa diminished to give an inactive enzyme the agent reduces some of disulfide bridge s in an area of the structure that is newly exposed area because of the cold inactivation. Such an area is unavailable if carboxypeptidase Y is in its native conformation. Because all the disulfide bridges in carboxypeptidase Y locate near the active site cleft it is suggested that the structural destruction if any occurs preferentially in this disulfide rich area. A possible mechanism of pressure-dependent cold inactivation of CPY is to destroy the a-helix rich region which creates an hydrophobic environment. This destruction is probably a result of the reallocation of water molecules. Experiments carried out in the presence of denaturing agents SDS urea GdnHCl salts glycerol and sucrose led to a conclusion consistent with the idea of water reallocation. Keywords high hydrostatic pressure cold

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