Carboxylic ester hydrolases from hyperthermophiles

Abstract

Carboxylic ester hydrolyzing enzymes constitute a large group of enzymes that are able to catalyze the hydrolysis, synthesis or transesterification of an ester bond. They can be found in all three domains of life, including the group of hyperthermophilic bacteria and archaea. Esterases from the latter group often exhibit a high intrinsic stability, which makes them of interest them for various biotechnological applications. In this review, we aim to give an overview of all characterized carboxylic ester hydrolases from hyperthermophilic microorganisms and provide details on their substrate specificity, kinetics, optimal catalytic conditions, and stability. Approaches for the discovery of new carboxylic ester hydrolases are described. Special attention is given to the currently characterized hyperthermophilic enzymes with respect to their biochemical properties, 3D structure, and classification.

Fig. 1

Reactions catalyzed by carboxylic ester hydrolases: a hydrolysis, b esterification, and c transesterification

Fig. 2

Substrates commonly used to test for esterase activity: ap-nitrophenyl butyrate, b 4-methylumbelliferyl butyrate, c (R/S)-ketoprofen methyl ester, and dp-nitrophenyl diethyl phosphate

Fig. 3

Canonical fold of α/β-hydrolases. a Topology diagram, with the strands indicated by red arrows and the helices by cyan cylinders. The positions of the catalytic residues are indicated. b–d The structures of three hyperthermophilic esterases: b the carboxylesterase AFEST from A. fulgidus (pdb 1JJI), c the esterase EstA from T. maritima (pdb 3DOH), and d the acylpeptide hydrolase apAPH from A. pernix (pdb 1VE6)