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Table 1 Comparison of isomerase/epimerase activities on CsCE Y114X mutants at 37 and 65 °C

From: Rational modification of substrate binding site by structure-based engineering of a cellobiose 2-epimerase in Caldicellulosiruptor saccharolyticus

Amino acid substituted in Y114

37 °C

65 °Ca

Isomerase activity (mM/min μg)

Epimerase activity (mM/min μg)

Isomerase activity (mM/min μg)

Epimerase activity (mM/min μg)

Y (parent)

15.6 ± 1.2

138 ± 2.3

187 ± 4.2

37.0 ± 3.6

V

9.74 ± 1.4

nd

29.2 ± 3.3

nd

N

5.84 ± 0.71

nd

9.73 ± 2.2

nd

S

1.95 ± 0.39

nd

17.5 ± 4.0

nd

A

9.74 ± 2.0

nd

25.3 ± 3.2

nd

K

9.74 ± 0.98

nd

15.6 ± 2.1

nd

G

3.90 ± 1.3

nd

15.6 ± 2.2

nd

D

11.7 ± 1.9

nd

17.5 ± 2.1

nd

C

5.84 ± 1.0

nd

15.6 ± 1.9

nd

L

nd

nd

29.2 ± 2.6

nd

E

17.5 ± 2.3

nd

208 ± 3.9

11.7 ± 2.2

P

1.95 ± 0.55

nd

17.5 ± 1.2

nd

I

7.79 ± 1.9

nd

17.5 ± 1.1

nd

W

nd

nd

11.7 ± 1.2

nd

T

3.90 ± 0.2

nd

7.81 ± 2.1

nd

R

nd

nd

13.6 ± 1.0

nd

F

1.95 ± 0.13

9.74 ± 2.1

48.7 ± 3.2

9.77 ± 3.2

M

3.90 ± 0.22

nd

17.5 ± 2.9

nd

Q

1.92 ± 0.08

nd

23.4 ± 3.4

nd

H

nd

nd

15.6 ± 2.8

nd

  1. Isomerase and epimerase activities were measured by quantifying lactulose and epilactose which were converted from 20 g/l lactose for 30 min at testing temperature. Values are mean ± SD measured from three experimental replicates
  2. nd, not detected
  3. aUnder this condition, lactulose formed by non-enzymatic isomerization was negligible
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Microbial Cell Factories

ISSN: 1475-2859

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