Crystal structures of two coupled enzymes accomplishing high-efficient biochemical synthesis of trehalose

Okazaki, Nobuo; Tamada, Taro; Miura, Yutaka*; Feese, M. D.*; Kato, Masaru*; Komeda, Toshihiro*; Takehara, Kyoko*; Kobayashi, Kazuo*; Kondo, Keiji*; Kuroki, Ryota

The crystal structure of glycosyltrehalose synthase (GTSase) from the hyperthermophilic archaeum Sulfolobus shibatae DSM5389 has been determined to 2.3 A resolution by X-ray crystallography. GTSase converts the glucosidic bond between the last two glucose residues of amylose from an alpha-1,4 bond to an alpha-1,1 bond, making a non-reducing glycosyl trehaloside in the first step of the biosynthesis of trehalose. The structure of GTSase can be divided into five domains. The central domain has the (beta/alpha)8 barrel fold which is conserved in the alpha-amylase family as the catalytic domain. Three invariant catalytic carboxylic amino acids in the alpha-amylase family are also found in GTSase at positions Asp241, Glu269 and Asp460 in the (beta/alpha)8 domain. Our previous study with KM1-GTSase has been shown that the maltooligosaccharides are converted to glycosyltrehalose by an intramolecular transglycosylation mechanism.