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A Zinc‐Dependent Alcohol Dehydrogenase (ADH) from Thauera aromatica , Reducing Cyclic α‐ and β‐Diketones
Author(s) -
Loderer Christoph,
Morgenstern Frances,
AnsorgeSchumacher Marion
Publication year - 2015
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201500171
Subject(s) - chemistry , alcohol dehydrogenase , biocatalysis , zinc , dehydrogenase , stereochemistry , alcohol , residue (chemistry) , substrate (aquarium) , enzyme , active site , combinatorial chemistry , organic chemistry , catalysis , reaction mechanism , oceanography , geology
Zinc‐dependent alcohol dehydrogenases (ADHs) are valuable biocatalysts for the synthesis of chiral hydroxy compounds such as α‐hydroxy ketones and diols, both valuable precursors for the synthesis of various pharmaceuticals. However, while highly active on aliphatic or phenyl‐substituted diketones, most well characterized ADHs show no significant activity on cyclic α‐ and β‐diketones. Therefore, this study aimed at the detection of a novel ADH capable to reduce these special targets. It involved a rational screening of biochemical pathways for enzymes with structurally related natural substrates. The so detected 6‐hydroxycyclohex‐1‐ene‐1‐carbonyl‐CoA dehydrogenase (ThaADH) from Thauera aromatica was cloned, expressed in Escherichia coli and purified by affinity chromatography. The characterization revealed a substrate specificity with highest activities on cyclic α‐ and β‐diketones including 1,2‐cyclohexanedione and 1,3‐cyclopentanedione. Structural reasons for this extraordinary substrate spectrum were investigated with a homology model created via Swiss Model server. Although the quality of the model may be improved, it suggests that a bulky aromatic residue, that plays a crucial role in the definition of the substrate binding pockets of most ADHs, is replaced by a glycine residue in ThaADH. We propose that this structural difference leads to the formation of one large binding pocket instead of two smaller ones and consequently to a preference for cyclic diketones over linear bulky substrates. Thus, we have achieved both provision of a novel biocatalyst with high potential in chiral synthesis, and a possible explanation for the measured differences to known ADHs. The described structural motif might be used for identification of further enzymes with a related substrate scope.