Table 1 Enzyme activity and thermal stability.

From: Determinants of ligand binding and catalytic activity in the myelin enzyme 2′,3′-cyclic nucleotide 3′-phosphodiesterase

variant

Phosphodiesterase activity (2′,3′-cNADP+ → 2′-NADP+)

Tm

kcat (s−1)

KM (μM)

kcat/KM(s−1 μM−1)

°C

Wild type*,**

940 ± 38

553 ± 46

1.70

58.0

H230Q**

24 ± 15

1055 ± 1130

0.02

55.0

H309Q**

–

–

–

52.7

H230S**

14 ± 14

1305 ± 2004

0.01

56.0

H309S**

21 ± 16

1192 ± 1468

0.02

57.3

H230Q & H309Q**

–

–

–

49.7

F235A

183 ± 15

6253 ± 798

0.03

53.0

F235L

221 ± 15

3788 ± 434

0.06

55.3

T232A

231 ± 136

39648 ± 25605

< 0.01

57.7

T311A

–

–

–

56.0

R307Q

1182 ± 205

2192 ± 548

0.54

59.0

V321A**

732 ± 33

1045 ± 77

0.70

59.5

Y168A

237 ± 7

1879 ± 122

0.13

53.7

Y168S

887 ± 98

1385 ± 235

0.64

53.7

P225G

1420 ± 60

483 ± 44

2.94

57.0

P296G

1332 ± 50

722 ± 51

1.73

60.0

Protein, solvent

kcat (s−1)

K M (μM)

kcat/KM (s−1 μM−1)

° C

CNPcat, H2O*

807 ± 52

423 ± 76

1.91

60.0

CNPcat, D2O

273 ± 19

147 ± 38

1.85

61.0

dCNPcat, H2O

893 ± 57

382 ± 70

2.34

58.0

dCNPcat, D2O

326 ± 27

204 ± 57

1.59

59.0

  1. All kcat and KM values are supplied with their respective standard errors. All Tm values were determined in the absence of ligands.
  2. *CNPcat and wild type here refer to the same protein, but the measured values have been determined at different times and therefore slightly vary from each other. The magnitude of variation is small.
  3. **The results have been discussed earlier (ref. 34) and are presented here for comparison.
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