Regioselective glucosylation of inositols catalyzed by Thermoanaerobacter sp. CGTase Alfonso Miranda-Molina a,b , Silvia Marquina-Bahena a , Agustín López-Munguía b , Laura Álvarez a,⇑ , Edmundo Castillo b,⇑ a Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos. Av. Universidad 1001, Col. Chamilpa, C.P. 62209, Cuernavaca, Morelos 62210, México b Departamento Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, Av. Universidad 2001, Col. Chamilpa, C.P. 62209, Cuernavaca, Morelos 62250, México article info Article history: Received 28 May 2012 Received in revised form 2 August 2012 Accepted 4 August 2012 Available online 14 August 2012 Keywords: CGTase Glucoamylase Inositols a-D-Glucosylation Regiopecificity Configuration abstract Monoglucosylated products of L-chiro-, D-chiro-, muco-, and allo-inositol were synthesized by regioselec- tive a-D-glucosylation with cyclodextrin glucosyl transferase from Thermoanaerobacter sp. after hydroly- sis of by products with Aspergillus niger glucoamylase. While the reactions carried out with D-chiro-, muco-, and allo-inositol resulted in the regioselective formation of monoglucosylated products, two prod- ucts were obtained in the reaction with L-chiro-inositol. Through the structural characterization of the glucosylated inositols here we demonstrated that the selectivity observed in the glucosylation of several inositols by Thermoanaerobacter sp. CGTase, is analogous to the specificity observed for the glucosylation of b-D-glucopyranose and equivalent glucosides. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Inositols (cyclohexanehexols) are sugar-like molecules with significant chemical and biological properties. Among all possible inositol stereoisomers, myo-inositol is the most prominent form, widely occurring in nature. Other naturally occurring isomers are scyllo-, neo-, D-chiro-, and muco-inositol. 1 The remaining three, epi-, allo-, L-chiro-, and cis-inositol are considered unnatural syn- thetic inositol isomers. 2,3 It has been reported that all inositol ster- eoisomers may be prepared from myo-inositol by inversion of the configuration (epimerization) of one or two of its hydroxyl groups. 4 In recent years, evidence of the physiological role of inositols and their glycosylated derivatives in cell functions has considerably increased the interests in these compounds for pharmaceutical applications. Indeed, it has been reported that glycosylphosphat- idylinositols (GPI) contribute to activate innate immune cells or to exert partial insulin-mimetic activity on glucose and lipid metabolism in insulin-sensitive cells (adipocytes, cardiomyocytes and diaphragms). 5,6 Moreover, phosphatidylinositol mannosides (PIMs), the components of mycobacterial cell walls, have demonstrated to be immunomodulators. 7 More recently, two series of new myo-inositol-derived glycolipid analogues were isolated from leaves of the Mexican medicinal plant Solanum lanceolatum, which demonstrated in vivo important anti-inflammatory activity. 8 Although, most of the glycosylated forms of inositols are natu- rally present in the vegetal kingdom, the low content in plants has limited their isolation and commercial application. 9 In order to cope with the lack of a convenient source of inositols, several chemical routes have been described for their synthesis. However, due to the similar reactivity of the multiple inositol hydroxyl groups, the regio- and stereo-selective glycosylations of these com- pounds remain a challenge in organic chemistry. 3 During the last two decades, biocatalysis has become an interesting alternative in organic synthesis due to the chemo-, regio-, and stereo-selectiv- ities of enzymes and their ability to carry out reactions in mild con- ditions. 10–17 Cyclodextrin glucosyl transferases (CGTase) (EC 2.4.1.19) are hexosyltransferase enzymes, produced extracellularly by a wide variety of bacteria, particularly Bacillus. The distinctive feature of these enzymes is the formation of cyclodextrins from starch through intra-molecular transglycosylation of a-D-(1?4)-linked D-glucose oligosaccharides, resulting in cyclization 18 Additionally, these enzymes also catalyze intermolecular transglycosylations involving disproportionation and hydrolysis of the amylose 0008-6215/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.carres.2012.08.002 ⇑ Corresponding authors. Tel./fax: +52 777 329 7997 (L.Á.); tel.: +52 777 56227609 (E.C.). E-mail addresses: lalvarez@ciq.uaem.mx (L. Álvarez), edmundo@ibt.unam.mx (E. Castillo). Carbohydrate Research 360 (2012) 93–101 Contents lists available at SciVerse ScienceDirect Carbohydrate Research journal homepage: www.elsevier.com/locate/carres