IMPLANTABLE HOLLOW-FIBER BIOREACTOR AS A POTENTIAL TREATMENT FOR HYPERCHOLESTEROLEMIA - CHARACTERIZATION OF THE CATALYTIC UNIT

Previous studies have shown that the modification of low density lipop rotein (LDL) by the enzyme phospholipase A(2) (PLA(2)) results in a re duction of cholesterol levels in the plasma of hypercholesterolemic ra bbits, due to accelerated clearance of the modified LDL. In the curren t study, we established techniques and optimized the ratio of enzyme t o support for the im mobilization of PLA(2) on a polymeric support. Ho llow fiber bioreactors made from polytetrafluoroethylene (PTFE) polyme rs were used to encapsulate immobilized PLA(2). This design was adopte d to eliminate hemolysis of red blood cells by the enzyme. Characteriz ation of the resulting immobilized enzyme in terms of its activity, Mi chaelis-Menten kinetic constants, and the variation of its activity wi th incubation time is presented. The enzyme activity was not significa ntly altered upon incubation at 37 degrees C in lipoprotein-deficient serum (LPDS), over the course of 2 months. The Michaelis-Menten kineti cs constants are K-M = 8.9 mM, V-max = 6434.2 for the free enzyme and K-M(app) = 16.7 mM, V-max(app), = 619.7 for the immobilized enzyme. Th ese data suggest that a system based on immobilized PLA, in conjunctio n with hollow fiber bioreactors (HFBs) may be a good candidate for low ering LDL levels in plasma. (C) 1995 John WiIey & Sons, Inc.