Phenylalanine ammonia-lyase immobilized in semipermeable microcapsules for enzyme replacement in phenylketonuria.

Phenylalanine ammonia-lyase immobilized within semipermeable microcapsules has an assayed enzyme activity which is 20% +/- 4% of the enzyme in free solution. The Km for the immobilized enzyme remained the same as that of the free enzyme. The pH optimum also remained unchanged at pH 8.5 +/- 1.0. At the lower pH range, enzyme activity is higher for the immobilized enzyme. Daily oral administration of microencapsulated phenylalanine ammonia-lyase to phenylketonuric rats decreased the systemic phenylalanine level by 35 +/- 8% in 2 days (P less than 0.05) and by 75 +/- 8% in 7 days (P less than 0.001).