Enzymatic Digestion of an Egg White Allergen, Lipocalin-type Prostaglandin D Synthase, and the Effect on Its Activity

Abstract

We have previously reported that lipocalin-type prostaglandin D synthase (L-PGDS) in egg white reacts with IgE from patients with egg allergies. We subsequently developed an immune complex transfer enzyme immunoassay for L-PGDS and found that the amount of L-PGDS in hen eggs varies depending on the hen lineage and other factors. L-PGDS catalyzes the conversion of prostaglandin (PG) H₂ to PGD₂ in the arachidonic acid cascade. Although chicken L-PGDS has enzymatic activity, its pH stability, digestibility and the relationship between its digestibility and activity are unclear. Here, we examined the digestibility of L-PGDS by pepsin and trypsin and the effect of digestion on its activity. L-PGDS activity was maintained after 30 min of pepsin digestion. However, after a further 2 h of trypsin digestion, the activity was below the detection limit. Pepsin and trypsin digests of L-PGDS were analyzed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. After 30 min of pepsin digestion, most of the L-PGDS remained at its native molecular weight. However, after 30 min of pepsin digestion, followed by 2 h of trypsin digestion, most of it was degraded from approximately 23 kDa to 13.5 kDa. These results are consistent with the enzyme activity results.