Organic solvents effect of the secondary structure of the araujiain hI, in different organic media

EVELINA QUIROGA; GERARDO CAMI; NESTOR CAFFINI; SONIA BARBERIS

BIOCHEMICAL ENGINEERING JOURNAL

Elsevier Science

Lugar: Amsterdan; Año: 2007

1369-703X

                The aim of this work was to carry out a comparative study of the secondary structure of araujiain hI (cystein plant protease) in aqueous-organic media (N,N-dimethylformamide (50%) and hexane (50%)) and in Tris-HCl buffer (0.1 M, pH 8), using FTIR spectroscopy.  The changes in the enzyme structure were correlated with the changes in the preferences and enzyme activities in such media.  The enzyme activity observed in the organic media was higher than those obtained in buffer.  Although the substrate preferences of araujiain hI exhibit different patterns in each medium, the enzyme always showed a high preference for glutamine derivative.  According to the study of the secondary structure, it was possible to conclude that a secondary structure with a high a-helical character was responsible for the highest activity of araujiain hI in the studied organic media.  Although the correlation between enzyme structure and catalytic activity requires direct measurement of active-site structure and of the effect of the reaction medium on the transition state of the reaction, it is clear that the noncovalent forces which maintain the native secondary structure of enzyme were modified when araujiain hI was suspended in such aqueous-organic media.