The influence of enzyme concentration on the encapsulation of glutamate dehydrogenase and alcohol dehydrogenase in red blood cells.

Glutamate dehydrogenase (GDH) and alcohol dehydrogenase (ADH) have been encapsulated in sheep and human red blood cells (RBCs) by a hypotonic dialysis/isotonic resealing procedure. At a fixed enzyme level in the dialysis bag (100 units/ml of RBCs), a significant encapsulation yield was observed for ADH, both in human (17.2%) and sheep (47.9%) RBCs, whereas a very low entrapment of GDH was achieved (1-3%) in either species. Carrier cell recovery was 61-65% in humans and 30-34% in sheep. Because of the aggregation of GDH to large polymers at protein levels above 1 mg/ml, the yield of encapsulation and the specific activity in human carrier RBCs were compared at different enzyme concentrations. While entrapment was not affected by differences in ADH up to 13,000 units/ml of RBCs (38 mg/ml), the yield of GDH encapsulation significantly decreased as the enzyme level increased up to 750 units/ml of RBCs (15 mg/ml), thus demonstrating the importance of protein concentration in the encapsulation process for those enzymes that tend to aggregate.