SITE-SPECIFIC MODIFICATION OF RABBIT MUSCLE ALDOLASE WITH FLUORESCENT-PROBES

The site-specific modification of rabbit muscle aldolase A by labeling of thiol residues of Cys-289 with 5-(2-((iodoacetyl)amino)ethyl)amino)naphthalene-1-sulfonic acid and Cys-239 with 5-iodoacetamidofluorescein or 4-dimethylamino-phenylazophenyl-4'-maleimide has been described. The method is based on the differences in kinetics of the chemical modification of aldolase thiols with the above reagents either in the presence or in the absence of a competitive inhibitor. The spectral properties of the doubly labeled aldolase derivatives were compared with those of the singly labeled enzyme. The doubly labeled aldolase derivatives exhibited full catalytic activity.