Understanding substrate specificity and enantioselectivity of carbonyl reductase from Candida parapsilosis ATCC 7330 (CpCR): Experimental and modeling studies

Microbial alcohol dehydrogenases: recent developments and applications in asymmetric synthesis

Alcohol dehydrogenases are a well-known group of enzymes in the class of oxidoreductases that use electron transfer cofactors such as NAD(P)+/NAD(P)H for oxidation or reduction reactions of alcohols or carbonyl compounds respectively. These enzymes are utilized mainly as purified enzymes and offer some advantages in terms of green chemistry. They are environmentally friendly and a sustainable alternative to traditional chemical synthesis of bulk and fine chemicals. Industry has implemented several whole-cell biocatalytic processes to synthesize pharmaceutically active ingredients by exploring the high selectivity of enzymes. Unlike the whole cell system where cofactor regeneration is well conserved within the cellular environment, purified enzymes require additional cofactors or a cofactor recycling system in the reaction, even though cleaner reactions can be carried out with fewer downstream work-up problems. The challenge of producing purified enzymes in large quantities has been solved in large part by the use of recombinant enzymes. Most importantly, recombinant enzymes find applications in many cascade biotransformations to produce several important chiral precursors. Inevitably, several dehydrogenases were engineered as mere recombinant enzymes could not meet the industrial requirements for substrate and stereoselectivity. In recent years, a significant number of engineered alcohol dehydrogenases have been employed in asymmetric synthesis in industry. In a parallel development, several enzymatic and non-enzymatic methods have been established for regenerating expensive cofactors (NAD+/NADP+) to make the overall enzymatic process more efficient and economically viable. In this review article, recent developments and applications of microbial alcohol dehydrogenases are summarized by emphasizing notable examples.

Construction of Bi-Enzyme Self-Assembly Clusters Based on SpyCatcher/SpyTag for the Efficient Biosynthesis of (R)-Ethyl 2-hydroxy-4-phenylbutyrate

Cascade reactions catalyzed by multi-enzyme systems are important in science and industry and can be used to synthesize drugs and nutrients. In this study, two types of macromolecules of bi-enzyme self-assembly clusters (BESCs) consisting of carbonyl reductase (CpCR) and glucose dehydrogenase (GDH) were examined. Stereoselective CpCR and GDH were successfully fused with SpyCatcher and SpyTag, respectively, to obtain four enzyme modules, namely: SpyCatcher-CpCR, SpyCatcher-GDH, SpyTag-CpCR, and SpyTag-GDH, which were covalently coupled in vitro to form two types of hydrogel-like BESCs: CpCR-SpyCatcher-SpyTag-GDH and GDH-SpyCatcher-SpyTag-CpCR. CpCR-SpyCatcher-SpyTag-GDH showed a better activity and efficiently converted ethyl 2-oxo-4-phenylbutyrate (OPBE) to ethyl(R)2-hydroxy-4-phenylbutanoate ((R)-HPBE), while regenerating NADPH. At 30 °C and pH 7, the conversion rate of OPBE with CpCR-SpyCatcher-SpyTag-GDH as a catalyst reached 99.9%, with the ee% of (R)-HPBE reaching above 99.9%. This conversion rate was 2.4 times higher than that obtained with the free bi-enzyme. The pH tolerance and temperature stability of the BESCs were also improved compared with those of the free enzymes. In conclusion, bi-enzyme assemblies were docked using SpyCatcher/SpyTag to produce BESCs with a special structure and excellent catalytic activity, improving the catalytic efficiency of the enzyme.

New insights into the stereospecific reduction by an (S) specific carbonyl reductase from Candida parapsilosis ATCC 7330: experimental and QM/MM studies

The quantum mechanics/molecular mechanics study of an (S) specific carbonyl reductase from C. parapsilosis ATCC 7330 showing a dual kinetic response for the reduction of ketones and α-ketoesters suggests different reaction mechanisms for the same.

Understanding (R) Specific Carbonyl Reductase from Candida parapsilosis ATCC 7330 [CpCR]: Substrate Scope, Kinetic Studies and the Role of Zinc

CpCR, an (R) specific carbonyl reductase, so named because it gave (R)-alcohols on asymmetric reduction of ketones and ketoesters, is a recombinantly expressed enzyme from Candida parapsilosis ATCC 7330. It turns out to be a better aldehyde reductase and catalyses cofactor (NADPH) specific reduction of aliphatic and aromatic aldehydes. Kinetics studies against benzaldehyde and 2,4-dichlorobenzaldehyde show that the enzyme affinity and rate of reaction change significantly upon substitution on the benzene ring of benzaldehyde. CpCR, an MDR (medium chain reductase/dehydrogenase) containing both structural and catalytic Zn atoms, exists as a dimer, unlike the (S) specific reductase (SRED) from the same yeast which can exist in both dimeric and tetrameric forms. Divalent metal salts inhibit the enzyme even at nanomolar concentrations. EDTA chelation decreases CpCR activity. However, chelation done after the enzyme is pre-incubated with the NADPH retains most of the activity implying that Zn removal is largely prevented by the formation of the enzyme-cofactor complex.