N-Acetylneuraminic acid is a nine-carbon, sialic acid monosaccharide commonly found in glycoproteins on cell membranes and in glycolipids such as gangliosides in mammalian cells. Studies suggest that N-Acetylneuraminic acid is useful biologically in neurotransmission, leukocyte extravasation, viral or bacterial infections and carbohydrate-protein recognition. It is believed that this negatively charged, non-reducing sugar is more difficult to analyze directly. One method for its detection in serum is to cleave pyruvic acid from the molecule via N-acetylneuraminic acid aldolase followed by colorimetric detection.