Discovery of a novel thermostable Zn2+ -dependent alcohol dehydrogenase from Chloroflexus aurantiacus through conserved domains mining

Abstract

Aims: The purpose of the study was to demonstrate feasibility of the Conserved Domains Database (CDD) for identification of novel biocatalysts with desirable properties from a class of well-characterized biocatalysts.

Methods and results: The thermostable ADH from Sulfolobus solfataricus with a broad substrate range was applied as a template for the search for novel thermostable ADHs via CDD. From the resulting hits, a putative ADH gene from the thermophilic organism Chloroflexus aurantiacus was cloned and expressed in Escherichia coli. The resulting enzyme was purified and characterized. With a temperature activity optimum of 70°C and a broad substrate spectrum especially for diketones, a versatile new biocatalyst was obtained.

Conclusions: Database-based mining in CDD is a suitable approach to obtain novel biocatalysts with desirable properties. Thereby, the available diversity of similar but not equal enzymes within this class can be increased.

Significance and impact of the study: For industrial applications, there is a demand for larger diversity of similar well-characterized enzymes in order to test them for a given process (biodiversity screening). For fundamental science, the comparison of enzymes with similar function but different sequence can provide insight into structure function relationships or the evolution of enzymes. This study gives a good example on how this demand can be efficiently met.

Keywords: Chloroflexus aurantiacus; alcohol dehydrogenase; biocatalysis; biodiversity screening; carbonyl reduction.