Impurities detected and identified in commercial PLBD2 and CHO PLBD2
To explain and understand the lipase activity observed when incubating recombinant human PLBD2 or CHO PLBD2 with polysorbates, proteomics analysis was conducted to identify potential contaminant lipase(s)/esterase(s) present in the human PLBD2 and CHO PLBD2 samples. Results showed that 1600 host cell proteins were present in the human PLBD2 sample. Among these HCPs, 11 of them were proteins with potential lipase activity as listed in Table 2. One or more of those lipases may contribute to polysorbate degradation. In the CHO PLBD2 sample, 91 host cell proteins were identified, including the group XV phospholipase A2 (LPLA2), which was the lipase previously shown to degrade polysorbate by Hall, et. al(Hall et al., 2016), as suggested by high confidence identification (16 unique peptides) of this protein in our proteomics analysis (Table 3). LPLA2 was almost exclusively identified, presenting at 0.14% relative to synthetic PLBD2, and showed the exact degradation pattern of PS20 and PS80 as suggested in the literature(Hall et al., 2016).