Cloning and expression of the human N-acetylneuraminic acid phosphate synthase gene with 2-keto-3-deoxy-D-glycero-D-galacto-nononic acid biosyntheticability

Sialic acids participate in many important biological recognition events, y et eukaryotic sialic acid biosynthetic genes are not well characterized. In this study, we have identified a novel human gene based on homology to the Escherichia coil sialic acid synthase gene (neuB), The human gene is ubiqu itously expressed and encodes a 40-kDa enzyme. The gene partially restores sialic acid synthase activity in a neuB-negative mutant of E. coil and resu lts in N-acetylneuraminic acid (Neu5Ac) and 2-keto-3-deoxy-D-glycero-D-gala cto-nononic acid (KDN) production in insect cells upon recombinant baculovi rus infection. In vitro the human enzyme uses N-acetylmannosamine 6-phospha te and mannose 6-phosphate as substrates to generate phosphorylated forms o f Neu5Ac and KDN, respectively, but exhibits much higher activity toward th e Neu5Ac phosphate product.