We have previously demonstrated that Chinese hamster ovary (CHO) cell lysates harbor sialidase, pgalactosidase, p-hexosaminidase, and fucosidase activities that can accumulate extracellularly in CHO cell culture, thereby potentially leading t o extracellular modification of glycoprotein oligosaccharides. The sialidase activity in CHO cell lysates was surprisingly active and stable at pH 7.5, with a half-life of 57 h at 37Β°C.
We have extended this work to determine whether 293, NSO, or hybridoma cell lysates contain similar glycosidase activities. The pH-activity profiles of pgalactosidase and p-hexosaminidase in lysates of these three cell lines resemble the pH-activity profiles for these enzymes in CHO cell lysate, whereas the pHactivity profiles of sialidase and fucosidase appear to be cell-type dependent. Sialidase activities were relatively stable at pH 4.5 in 293, NSO, and hybridoma cell lysates. However, the activities in 293 and NSO cell lysates were unstable at pH 7.5, with no activity remaining after a 2-h incubation at 37Β°C. The sialidase activity in hybridoma cell lysate was moderately stable at pH 7.5 with 30% of the activity remaining after a 2-h incubation at 37Β°C. We conclude that the sialidase activities from 293, NSO, and hybridoma cells have characteristics similar to the vast majority of reported mammalian sialidase activities, and that these activities are markedly different from the CHO cell sialidase activity. Finally, sialidase, p-galactosidase, p-hexosaminidase, and fucosidase activities were measured at pH 7 in cell-free bioreactor supernatants of the hybridoma cell line. As previously observed in CHO cell culture, all four glycosidase activities were present in the hybridoma supernatants. However, the sialidase activity in hybridoma supernatant was an order of magnitude lower than in CHO cell culture supernatant despite the fact that the hybridoma cell lysis rate was an order of magnitude higher.