Biochemical Studies Of Otosclerosis: Phosphohydrolase Activity In Stapedial Footplates

Abstract

Pyrophosphate, adenosine triphosphate, and para-nitrophenylphosphate were used as substrates to determine phosphohydrolase activity on intact stapedial footplates from patients with and without otosclerosis. All phosphodydrolase activities were increased in otosclerosis, but the extent of the increase was different for each substrate. While the variation in the increase in activities in otosclerosis suggests three separate enzymes, the common properties of resistance to solubilization and similar stabilities as well as competitive inhibition between the substrates indicate a single catalytic protein with multiple phosphohydrolase activities. It appears that a qualitativc change in the alkaline phosphatase may be associated with otosclerosis. The altered enzyme could be the primary factor in the etiology of otosclerosis. More likely, the organic or inorganic pyrophosphatase activities of the increased enzyme may be significant in the accretion of otosclerotic bone during progression of the disease.