**4. Acknowledgment**

We thank Prof. Dr. Erden Banoğlu (Gazi University, Faculty of Pharmacy, Ankara) for providing sample of Homothiomethisosildenafil which was also isolated from the herbal dietary supplement by him. Central Instrumental Analysis Lab. of Pharmacy, Faculty of Ankara University provided support for acquisition of the IR, NMR, HPLC-MS spectrometers and elemental analyzer used in this work.

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**4** 

*Japan* 

**Purification of Marine Bacterial** 

Toshiki Mine and Takeshi Yamamoto *Glycotechnology Business Unit, Japan Tobacco Inc.,* 

**Sialyltransferases and Sialyloligosaccharides** 

Sialic acids are important components of carbohydrate chains and are usually found at the terminal position of the carbohydrate moiety of glycoconjugates (Angata & Varki, 2002; Schauer, 2004). Sialyloligosaccharides of glycoconjugates play important roles in many biological processes (Gagneux & Varki, 1999; Varki, 1993). The transfer of sialic acids to carbohydrate chains is performed by specific sialyltransferases in the cell (Angata & Varki, 2002; Vimr et al., 2004). Thus, sialyltransferases are considered to be key enzymes in the biosynthesis of sialylated glycoconjugates. Detailed investigations of the biological functions of sialylated glycoconjugates require an abundant supply of the target compounds. To date, many sialyltransferases, and the genes encoding them, have been isolated from various sources including mammalian, bacterial, and viral sources (Schauer, 2004; Sujino et al., 2000; Yamamoto et al., 2006). During our research, we have isolated over 20 bacteria that produce sialyltransferase and have revealed the characteristics of these enzymes (Kajiwara et al., 2009; Yamamoto, 2010). In this chapter, we will introduce our research activities focusing on methods for (1) screening bacteria for glycosyltransferase activity; (2) purifying native sialyltransferases from marine bacteria; and (3) synthesizing and purifying

Sialic acid is a family of acidic monosaccharides comprising over 50 naturally occurring derivatives of neuraminic acid (5-amino-3,5-dideoxy-D-*glycero*-D-*galacto*-2-nonulosonic acid or Neu) (Angata & Varki, 2002; Vimr et al., 2004). Structurally, sialic acid is one of the more complicated naturally occurring monosaccharides and is based on a skeleton of nine carbons (Schauer, 2004). *N*-acetylneuraminic acid (Neu5Ac), *N*-glycolylneuraminic acid (Neu5Gc), and 2-keto-3-deoxy-D-*glycero*-D-*galacto*-nonulosonic acid (deaminoneuraminic acid, KDN), are the three most common members of this family (Angata & Varki, 2002; Schauer, 2004). The structure of Neu, Neu5Ac, Neu5Gc and KDN are shown in Figure 1. Although sialic acid is widely distributed in higher animals and some classes of microorganisms, only Neu5Ac is ubiquitous (Angata & Varki, 2004). Usually, sialic acid exists in the carbohydrate moiety of glycoconjugates, including glycoproteins and glycolipids, and is linked to the terminal positions of the carbohydrate chains of the glycoconjugates. Many studies have been carried out to clarify the structure-function relationship of carbohydrate chains containing sialic acid. These studies have revealed that Neu5Ac is the most common sialic acid component of carbohydrate chains and sialylated carbohydrate chains of

sialyloligosaccharides produced by marine bacterial sialyltransferases.

**1. Introduction** 

