The Sialic Acids

A specific kinase that catalyzed the phosphorylation of N-acyl-d-mannosamine in the presence of adenosine triphosphate was purified approximately 2000-fold from rat liver extracts. The enzyme was specific for ATP and either N-acetyl- or N-glycolyl-d-mannosamine. The results of fractionation, partial heat inactivation, and kinetic experiments indicated that a single enzyme was responsible for the phosphorylation of the two N-acylmannosamines. Mammalian tissue extracts (the soluble fractions) were assayed for the kinase and other enzymes involved in the metabolic pathway between the hexoses and sialic acids, and the kinase was detected in some of these extracts.