Structure and characterization of a NAD(P)H-dependent carbonyl reductase from Pseudomonas aeruginosa PAO1

Asymmetric synthesis of tert-butyl (3R,5S)-6-chloro-3,5-dihydroxyhexanoate using a self-sufficient biocatalyst based on carbonyl reductase and cofactor co-immobilization

tert-Butyl (3R,5S)-6-chloro-3,5-dihydroxyhexanoate [(3R,5S)-CDHH] is the key chiral intermediate to synthesize the side chain of the lipid-lowering drug rosuvastatin. Carbonyl reductases showed excellent activity for the biosynthesis of (3R,5S)-CDHH. The requirement of cofactor NADH/NADPH leads to high cost for the industrial application of carbonyl reductases. In this study, a self-sufficient biocatalyst based on carbonyl reductase and NADP⁺ co-immobilization strategy was developed on an amino resin carrier LX-1000HAA (SCR-NADP⁺@LX-1000HAA). The self-sufficient biocatalyst achieved in situ cofactor regeneration and showed the activity recovery of 77.93% and the specific activity of 70.45 U/g. Asymmetric synthesis of (3R,5S)-CDHH using SCR-NADP⁺@LX-1000HAA showed high enantioselectivity (> 99% e.e.) and yield (98.54%). Batch reactions were performed for ten cycles without extra addition of NADP⁺, and the total yield of (3R,5S)-CDHH achieved at 10.56 g/g biocatalyst. The present work demonstrated the potential of the self-sufficient biocatalyst for the asymmetric biosynthesis of rosuvastatin intermediate.

Biochemical and structural investigation of sulfoacetaldehyde reductase from Klebsiella oxytoca

Sulfoacetaldehyde reductase (IsfD) is a member of the short-chain dehydrogenase/reductase (SDR) family, involved in nitrogen assimilation from aminoethylsulfonate (taurine) in certain environmental and human commensal bacteria. IsfD catalyzes the reversible NADPH-dependent reduction of sulfoacetaldehyde, which is generated by transamination of taurine, forming hydroxyethylsulfonate (isethionate) as a waste product. In the present study, the crystal structure of Klebsiella oxytoca IsfD in a ternary complex with NADPH and isethionate was solved at 2.8 Å, revealing residues important for substrate binding. IsfD forms a homotetramer in both crystal and solution states, with the C-terminal tail of each subunit interacting with the C-terminal tail of the diagonally opposite subunit, forming an antiparallel β sheet that constitutes part of the substrate-binding site. The sulfonate group of isethionate is stabilized by a hydrogen bond network formed by the residues Y148, R195, Q244 and a water molecule. In addition, F249 from the diagonal subunit restrains the conformation of Y148 to further stabilize the orientation of the sulfonate group. Mutation of any of these four residues into alanine resulted in a complete loss of catalytic activity for isethionate oxidation. Biochemical investigations of the substrate scope of IsfD, and bioinformatics analysis of IsfD homologs, suggest that IsfD is related to the promiscuous 3-hydroxyacid dehydrogenases with diverse metabolic functions.

A protein complex bearing an oxidase with napthalene dihydrodiol dehydrogenase activity is induced in Mucor circinelloides strain YR-1 during growth on polycyclic aromatic compounds

Fungi are organisms capable of growing in a myriad of conditions and respond to counteract environmental cues. Several locations in the world are polluted with oil and its derivatives, and some microorganisms tolerant to these compounds have been isolated. Some fungi can grow in the presence of molecules such as polycyclic aromatic hydrocarbons as sole carbon sources. In this report, we further characterized the induced enzymes with phenanthrene from Mucor circinelloides YR-1 strain, isolated from a polluted field near a petrochemical facility in México. We identified a putative oxidase that is induced when growth with phenanthrene as sole carbon source at a pH of 8.5 and is NADP⁺ dependent. We show that this enzyme bears naphthalene dihydrodiol dehydrogenase activity with substrate preference for the cis-naphthalene over the trans-naphthalene, with an optimal pH in the range of 8-10. Mass spectrometry analysis revealed that the induced enzyme belongs to the NADP⁺ oxidase family enzymes with the typical Rossmann-fold for NADP⁺ binding. This enzyme seems to form a high molecular weight structure (~ 541 kDa) and with a monomer of 57 kDa, suggesting that the multimer is constituted of 10 subunits. Our findings contribute to understanding of the roles that dihydrodiol dehydrogenases have in organisms exposed to toxic compounds in the environment and can regulate their expression.