ROLE OF TYROSINE RESIDUES ON STRUCTURE‐FUNCTION OF FRUCTOSE‐1,6‐BIPHOSPHATE ALDOLASE FROM CERATITIS CAPITATA

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Abstract
Tyrosine contributions to the structure‐function relationship in the fructose‐1, 6‐biphospate aldolase from C. capitata have been investigated. There are three well defined groups of tyrosine residues with different roles in the structure of the insect aldolase. C‐terminal tyrosine residues are essential for the maintenance of the catalytic conformation. Releasing of these residues by carboxypeptidase A treatment results in complex conformational changes according to CD studies. Another tyrosine residue group is located at the active site, and the substrate, fructose‐1,6‐biphosphate, protects it upon nitration. Chemical modification of this residue results in enzyme activity changes similar to those induced by carboxypeptidase digestion. Enzyme‐substrate interaction results in a change of the microenvironment of at least three tyrosine residues per subunit with different accessibility for tetranitromethane.