Activation of cathepsin D by polyanionic compounds.
We examined the nature of the activation of cathepsin D by polyanionic compounds. Tripolyphosphate, a model compound for polyanions, decreased the Km value of porcine cathepsin D for bovine serum albumin without affecting VMAX. Half-maximal activation was achieved at 0.2 mM free tripolyphosphate. Electrophoretic mobility of cathepsin D decreased as the tripolyphosphate concentration was increased, and the enzyme had no net charge at 50 mM triP. The concentration for the half-maximal mobility change of cathepsin D (0.18 mM) was similar to that for half-maximal activation. These results suggest that tripolyphosphate increased affinity of the enzyme for its substrate by cancelling positive charges on cathepsin D and thus decreasing the electrostatic repulsion.
Watabe
S
S
Radioisotope Laboratory, Faculty of Agriculture, Yamaguchi University, Japan.
Ikeda
T
T
Yago
N
N
D000302:Adrenal Cortex / Q000201:enzymology; D000818:Animals; D002402:Cathepsin D / Q000378:metabolism*; D002417:Cattle; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D007700:Kinetics; D013552:Swine
D002402:Cathepsin D