Preparation of immobilized L-phenylalanine ammonia-lyase in tubular form for depletion of L-phenylalanine.

The enzyme L-phenylalanine ammonia-lyase (EC 4.3.1.5), which catalyzes the conversion of L-phenylalanine into trans-cinnamic acid, was adsorbed in the walls of asymmetric hollow fibers and covalently bound to the innerwall of small bore nylon tubing. Multi-tubular enzyme reactor cartridges were constructed both from hollow fibers and nylon tubes and the capacity of the reactors to degrade phenylalanine at physiological concentrations was evaluated in perfusion studies at different flow rates ranging from 30 to 80 ml/min. Hollow fiber enzyme reactors showed significantly higher activity than nylon tube reactors of commensurable dimensions and this finding is attributed to the difficulties in immobilizing L-phenylalanine ammonia-lyase via covalent linkages. The results suggest that extracorporeal use of such multi-tubular enzyme reactors offer a promising approach to deplete serum phenylalanine levels.