Chapter 2
Biocatalytic Applications
2.1 Hydrolytic Reactions
Of all the types of enzyme-catalyzed reactions, hydrolytic transformations involving amide and ester bonds are the easiest to perform using proteases, esterases, or
lipases. The key features that have made hydrolases the favorite class of enzymes
for organic chemists during the past two decades are their lack of sensitive cofactors
(which otherwise would need to be recycled) and the large number of readily
available enzymes possessing relaxed substrate specificities to choose from.
About half of the total research in the field of biotransformations has been
performed using hydrolytic enzymes of this type [1, 2]. The reversal of the reaction,
giving rise to ester or amide synthesis, has been particularly well investigated using
enzymes in organic solvent systems. The special methodologies involved in this
latter type of reaction are described in Sect. 3.1.
Other applications of hydrolases, such as those involving the formation and/or
cleavage of phosphate esters, epoxides, nitriles, and organo-halides, are described
in separate chapters.
2.1.1 Mechanistic and Kinetic Aspects
The mechanism of amide- and ester-hydrolyzing enzymes is very similar to that
observed in the chemical hydrolysis by a base. A nucleophilic group from the active
site of the enzyme attacks the carbonyl group of the substrate ester or amide. This
nucleophilic ‘chemical operator’ can be either the hydroxy group of a serine (e.g.,
pig liver esterase, subtilisin, and the majority of microbial lipases), a carboxylate
group of an aspartic acid (e.g., pepsin) [3], or the thiol functionality of cysteine
(e.g., papain) [4–6].
© Springer International Publishing AG 2018
K. Faber, Biotransformations in Organic Chemistry,
DOI 10.1007/978-3-319-61590-5_2
31
Biocatalytic Applications
2.1 Hydrolytic Reactions
Of all the types of enzyme-catalyzed reactions, hydrolytic transformations involving amide and ester bonds are the easiest to perform using proteases, esterases, or
lipases. The key features that have made hydrolases the favorite class of enzymes
for organic chemists during the past two decades are their lack of sensitive cofactors
(which otherwise would need to be recycled) and the large number of readily
available enzymes possessing relaxed substrate specificities to choose from.
About half of the total research in the field of biotransformations has been
performed using hydrolytic enzymes of this type [1, 2]. The reversal of the reaction,
giving rise to ester or amide synthesis, has been particularly well investigated using
enzymes in organic solvent systems. The special methodologies involved in this
latter type of reaction are described in Sect. 3.1.
Other applications of hydrolases, such as those involving the formation and/or
cleavage of phosphate esters, epoxides, nitriles, and organo-halides, are described
in separate chapters.
2.1.1 Mechanistic and Kinetic Aspects
The mechanism of amide- and ester-hydrolyzing enzymes is very similar to that
observed in the chemical hydrolysis by a base. A nucleophilic group from the active
site of the enzyme attacks the carbonyl group of the substrate ester or amide. This
nucleophilic ‘chemical operator’ can be either the hydroxy group of a serine (e.g.,
pig liver esterase, subtilisin, and the majority of microbial lipases), a carboxylate
group of an aspartic acid (e.g., pepsin) [3], or the thiol functionality of cysteine
(e.g., papain) [4–6].
© Springer International Publishing AG 2018
K. Faber, Biotransformations in Organic Chemistry,
DOI 10.1007/978-3-319-61590-5_2
31