A computational approach to solvent-free synthesis of ethyl oleate using Candida rugosa and Candida antarctica B lipases I-Interfacial activation and substrate-ethanol, oleic acid- adsorption.

MARÍA LAURA FORESTI; MARÍA LUJÁN FERREIRA

BIOMACROMOLECULES

Año: 2004 vol. 5 p. 2366 - 2375

1525-7797

This paper presents the results of a MM2 study of the adsorption of oleic acid and ethanol/water in the tunnel and active site models of lipases from Candida rugosa and Candida antarctica B. The role of an interface polar/no polar in the opening of Candida rugosa lipase’s lid is also addressed, discussed and analysed at the level of the conformational changes needed to achieve the lipase open form. The adsorption of oleic acid and alcohols considering Candida antarctica B, a lipase not interfacially activated, is also presented. In this case, the tunnel is shorter than in case of Candida rugosa lipase. Two different pockets can be visualised at the active site-tunnel model of Candida antarctica B lipase: one for the acyl group and another for the alcohol. Wrong location of alcohol and oleic acid severely hinders reaction because it hinders the H-transfer to histidine, a key step in the reaction mechanism. Right location of alcohol decreases the possibility of alcohol inhibition. In the case of Candida rugosa, no restrictions for ethanol/water location are found. For that lipase, a second adsorption site for oleic acid (outside the tunnel) is presented. This site is the exit tunnel of the ester product when oleic acid is adsorbed in the tunnel. Experimental results of our own that correlate with this study are presented.