Enantiomeric Resolution of 2-Aryl Propionic Esters with Hyperthermophilic and Mesophilic Esterases:  Contrasting Thermodynamic Mechanisms

Abstract

The enantiomeric resolution of 2-aryl propionic esters by hyperthermophilic and mesophilic esterases was found to be governed by contrasting thermodynamic mechanisms. Entropic contributions predominated for mesophilic esterases from Candida rugosa and Rhizomucor miehei, while enthalpic forces controlled this resolution by the esterase from the extremely thermoacidophilic archaeon, Sulfolobus solfataricus P1. This disparity in thermodynamic mechanism can be attributed to the differences in conformational flexibility of mesophilic and thermophilic enzymes as they relate to the temperature range (4-70 degrees C) examined.

Carboxylic ester hydrolases from hyperthermophiles

“…The enzyme hydrolyzed the ( R )-ester of racemic ketoprofen methylester and showed an enantiomeric excess of 80% with a conversion rate of 20% in 32 h. In another study, the esterase Sso-Est1 from S. solfataricus P1 (Sehgal et al 2001 ) was identified as homolog to the mesophilic Bacillus subtilis ThaiI-8 esterase (CNP) (Quax and Broekhuizen 1994 ) and Candida rugosa lipase (CRL) (Lee et al 2001 ), which are used for the chiral separation of racemic mixtures of 2-arylpropionic methyl esters. The enzyme was characterized biochemically for its ability to resolve mixtures of ( R,S )-naproxen methyl ester under a variety of reaction environments (Sehgal and Kelly 2002 , 2003 ). Sso-Est1 showed a specific reaction toward the ( S )-naproxen ester in co-solvent reaction conditions with an enantiomeric excess of ≥90%.…”

Effect of temperature on the stereoselectivity of phospholipase D toward glycerol in the transphosphatidylation of phosphatidylcholine to phosphatidylglycerol

“…On the other hand, the stereochemical purity of a chiral substance is often evaluated by the E value (11,12,14,15,17), meaning the enantiospecificity ratio. Defining E as the diastereospecificity ratio for the R,R and R,S diastereomers, it is expressed as Equation 5…”

“…The negative ∆∆S ‡ values indicate that the R,R isomer is more tightly bound to the enzyme in the transition state than is the R,S isomer. This is presumably due to favorable van der Waals interactions and hydrogen bonding between the R,R isomer and the amino acid side chains lining the binding sites in the complex (13,15).…”

“…On the other hand, Sakai et al (11,12) have reported a low-temperature method (−40°C at best) for enhancing enantioselectivity in lipase-catalyzed kinetic resolutions of some chiral alcohols. Other studies have shown that temperature can affect the enantioslectivity of dehydrogenases and esterases (13)(14)(15). To examine this observation further and to test its applicability to transphosphatidylation, we determined the effect of temperature on the course of the stereochemical reaction of several PLD enzymes from Actinomyces and from cabbage in the range of 0 to 60°C.…”

Extremophiles and their Application to Biofuel Research

“…Thermophilic examples include enzymes described for Thermoanaerobacter spp. (Royter et al, 2009;Rao et al, 2011) and the archaeal genus Sulfolobus (Huddleston et al, 1995;Sehgal and Kelly, 2002;Ejima et al, 2004;Mandrich et al, 2007). Commercial use of psychrophilic lipases (Huston, 2008;Cavicchioli et al, 2010) has been moderate save for a few well-known examples such as the Candida antarctica lipases available from Sigma Aldrich and Novozymes.…”