pK and pl Values of Amino Acids

Name

pK

pI

at 25°C

pK

α-CO2H

pK

NH3

pK

R-group

Alanine

2.35

9.87

 

6.11

Arginine

2.18

9.09

13.2

10.76

Asparagine

2.18

9.09

13.2

10.76

Aspartic Acid

1.88

9.60

3.65

2.98

Cysteine

1.71

10.78

8.33

5.02

Glutamic Acid

2.19

9.67

4.25

3.08

Glutamine

2.17

9.13

 

5.65

Glycine

2.34

9.60

 

6.06

Histidine

1.78

8.97

5.97

7.64

Isoleucine

2.32

9.76

 

6.04

Leucine

2.36

9.60

 

6.04

Lysine

2.20

8.90

10.28

9.47

Methionine

2.28

9.21

 

5.74

Phenylalanine

2.58

9.24

 

5.91

Proline

1.99

10.60

 

6.30

Serine

2.21

9.15

 

5.68

Threonine

2.15

9.12

 

5.60

Tryptophan

2.38

9.39

 

5.88

Tyrosine

2.20

9.11

10.07

5.63

Valine

2.29

9.74

 

6.02