The Kinetics of Plasma Aspirin Esterase in Relation to Old Age and Frailty

: The kinetics of the phase I enzyme aspirin esterase were estimated in plasma from ten young volunteers, seven healthy elderly volunteers, and in ten frail elderly subjects. Maximal reaction velocity at enzyme saturation (vmax) was similar in young and healthy elderly volunteers, but was significantly reduced in the frail elderly. The Michaelis constant (Km) was similar in all three groups. The results suggest that impaired in vitro aspirin metabolism in frail elderly people is due to a reduction in the quantity of enzyme present, rather than a qualitative change in enzyme proteins.