Purification and properties of fructose diphosphate aldolase from Boa constrictor constrictors

Fructose diphosphate aldolase from the muscles of Boa constrictor constrictors has been purified and obtained in the crystalline form. The substrate specificity and catalytic activity are similar to those of rabbit muscle aldolase, although there are significant differences in amino acid composition. The enzyme shows a pronounced change in absorption at 278 mμ on heating with a transition temperature of 59.5 °; this is shifted to 63.5 ° in the presence of the substrate. Studies of the heat stability suggest that the “melted-out” form of the enzyme undergoes further irreversible change, with loss of enzyme activity. The protein has a molecular weight of 153,000 and appears to contain three C-terminal tyrosine residues. Labeling of the active sites with radioactive dihydroxyacetone phosphate is consistent with a three-chain model. However, prolonged exposure at pH 2.4 leads to further changes in sedimentation properties suggesting the presence of smaller subunits.