Discovery of a new NADPH-dependent aldo-keto reductase from Candida orthopsilosis catalyzing the stereospecific synthesis of (R)-pantolactone by genome mining

( R )-Pantolactone (PL) is a key chiral intermediate for the synthesis of calcium ( R )-pantothenate and ( R )-panthenol used as food additives. The commercial production of ( R )-pantothenate is performed by the resolution of racemic pantothenate, which is synthesized through an aldol condensation and a cyanation reaction. In this study, we investigated another synthetic method of ( R )-pantothenate through the stereoselective reduction of ketopantoyl lactone (KPL) by aldo-keto reductase (AKR). A series of conjugated polyketone reductases (CPRs) were discovered from GenBank database by genome mining approach. The putative CPR gene from Candida orthopsilosis Co 90–125 ( Cor CPR) was cloned and functionally expressed in Escherichia coli BL21 (DE3). The optimum pH and temperature of recombinant Cor CPR were 6.0–7.0 and 40 ℃, respectively. The K m and v max toward KPL were1.3 mM and 227.3 μ mol/min/mg protein, respectively. The conserved sequences suggest that Cor CPR belongs to AKR3C family of AKR superfamily. Furthermore, a catalytic tetrad was proposed, and the detailed mechanism was clarified by molecular docking. In a batch reaction, 50 mM KPL was reduced to ( R )-PL with 99% conversion and > 99% enantiomeric excess within 5 h. The recombinant Cor CPR from C. orthopsilosis shows potential application in the asymmetric synthesis of ( R )-pantothenate preparation.