Sialic acid synthase (NANS, SAS) can convert N-acetylmannosamine 6-phosphate (ManNAc-6-P) to N-acetylneuraminate 9-phosphate (Neu5Ac-9-P) (Lawrence et al. 2000). NANS shows lower activity towards ManNAc and can convert it to Neu5Ac (not shown here, Lawrence et al. 2000).