Expression of 9-O- and 7,9-O-acetyl modified sialic acid in cells and their effects on influenza viruses

Karen N. Barnard; Brian R. Wasik; Justin R. LaClair; Wendy S. Weichert; Brynn K. Lawrence; Colin R. Parrish

4 from which it has been observed to migrate to the C8 and C9 position under 66 physiological conditions, allowing the possible addition of another acetyl group to C7 (6, 67 7). A migrase enzyme has been proposed to aid in the transfer of the acetyl group from 68 C7 to C9, however a specific enzyme has yet to be identified (5, 8, 9) . CasD1 is 69 localized in the late Golgi, so acetyl modifications are added during the later stages of 70 protein glycosylation. The regulatory processes that control the number of acetyl groups 71 added or their positions have not been well defined, although clear differences in 72 expression of 7,9-O-Ac and 9-O-Ac have been reported in mouse and human tissues, 73 chicken embryos, and some other animals (10, 11). CasD1 uses acetyl-CoA and likely 74 has a preference for CMP-Neu5Ac as a substrate, so that it is less active on CMP-75 Neu5Gc (7). The existence of an enzyme to facilitate the migration of acetyl groups from 76 C7 has been proposed, but not identified (5). 77