CONFORMATIONAL STABILITY OF FRUCTOSE‐1,6‐BIPHOSPHATE ALDOLASE FROM CERATITIS CAPITATA

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Abstract
Fructose 1,6-biphosphate aldolase from Ceratitis capitata is a tetramer of identical subunits with 34% α-helix, 22% β structure and 44% of aperiodic order. Increase of urea concentration up to 4.0 M results in non-cooperative reversible dissociation of the enzyme. Sodium dodecylsulphate 0.06% (w/v) dissociates the tetramer cooperatively with retention of the helical content. Thermal denaturation was a non-reversible cooperative process with a midpoint for the transition at 55°. Cysteine residues are involved in this process and 2-mercapto-ethanol preserves partially the enzyme activity. The acidic dissociation of the enzyme is a non-reversible process in contrast to the reversible basic dissociation. Increase of ionic strength results in a more ordered secondary structure for the monomer after acidic dissociation.