Microbial alkyl- and aryl-sulfatases: mechanism, occurrence, screening and stereoselectivities

Abstract

This review gives an overview on the occurrence of sulfatases in Prokaryota, Eukaryota and Archaea. The mechanism of enzymes acting with retention or inversion of configuration during sulfate ester hydrolysis is discussed taking two complementary examples. Methods for the discovery of novel alkyl sulfatases are described by way of sequence-based search and enzyme induction. A comprehensive list of organisms with their respective substrate scope regarding prim- and sec-alkyl sulfate esters allows to assess the capabilities and limitations of various biocatalysts employed as whole cell systems or as purified enzymes with respect to their activities and enantioselectivities. Methods for immobilization and selectivity enhancement by addition of metal ions or organic (co)solvents are summarised.

Scheme 1

Stereochemical consequences of catalysis by retaining and inverting hydrolases, i.e., dehalogenases, epoxide hydrolases, glycosidases and sulfatases

Fig. 1

Catalytic residues and their mode of action for the retaining sulfatase PAS from Pseudomonas aeruginosa (PDB 1HDH, top left) and the inverting sulfatase Pisa1 from P. sp. DSM 6611 (PDB 4AXH, top right). Preferred enantiomers of the substrate 2-octyl sulfate (green) were docked into the active site using Schrödinger Maestro (Schrödinger Maestro Software Suite 2013) The flow of electrons implying nucleophilic attack is indicated by red arrows, and the S–O/C–O bonds being broken are marked by scissor symbols. The schematic mechanism is given below. Some amino acid residues were omitted for clarity. Pictures were generated using Pymol (Pymol Software 2013)

Scheme 2

Partial sequence alignment of SUMF1 gene derived proteins. PJDR2, Paenibacillus sp. JDR-2 (YP_003009726); CM, Cupriavidus metallidurans (YP_586663); AC, Acinetobacter calcoaceticus (YP_004994666); RS, putative FGE-protein from Ralstonia solanacearum RFBP2957 (YP_003747422); human (NP_877437); mouse (NP_666049); sea urchin (XP_782973). Sequence alignment was done with clustal omega (Sievers et al. 2011). Numbers in brackets indicate the aligned amino acid residues. Letters highlighted in bold display the conserved sequence across Eukaryota and Prokaryota