Semi-rational engineering an aldo–keto reductase for stereocomplementary reduction of α-keto amide compounds

Table 1 Alanine scanning of iolS for identifying the hotspots^a

Variants	ee (%)^b	Conv. (%)^c	Favored enantiomer
N21A	93.2 ± 0.5	97.3 ± 0.6	R
N27A	74.1 ± 0.3	56.4 ± 0.4	S
L28A	6.3 ± 0.2	43.6 ± 0.3	R
Y29A	4.2 ± 0.3	48.3 ± 0.4	R
I57A	64.5 ± 0.4	58.5 ± 0.7	S
H87A	1.5 ± 0.1	39.8 ± 0.4	S
F94A	71.3 ± 0.5	61.8 ± 0.2	S
F96A	75.2 ± 0.4	58.7 ± 0.6	S
F126A	15.1 ± 0.2	50.2 ± 0.4	R
N156A	76.7 ± 0.5	62.4 ± 0.5	S
Y203A	70.1 ± 0.4	54.2 ± 0.4	S
L226A	72.7 ± 0.3	64.4 ± 0.7	S

^aReaction condition: 4 mM substrate 1a, 200 mM glucose and 0.1 g wet whole-cell in potassium phosphate buffer (100 mM, pH 7.0, 500 μL) at 30 °C. Experiments were conducted in duplicate
^bThe ee values were measured by chiral HPLC; the absolute configuration was determined by comparing the retention times with literature data
^cConversions were determined by chiral HPLC analysis

ISSN: 1475-2859