Table III (p. 96) contains analytical data obtained by a refined method for the estimation in proteins of the three diamino-acids, arginin, histidin and lysin. This method was devised by Kossel. In skilful hands it yields very accurate results. It will be noted that the histidin content of plant proteins varies much less than does that of either arginin or lysin. Yet the extreme values for this constituent of the protein molecule range from 3.81 per cent in stizolobin, a globulin from the velvet bean, to 0.39 per cent in gliadin from rye. The content of arginin in different proteins varies in a surprising degree. Thus a globulin of buckwheat yields 23 per cent arginin, whereas zein of the maize kernel contains but 1.35 per cent. Among the vegetable proteins the yield of lysin is generally very low in comparison to that obtained from the proteins of animal tissues. The extreme limits of the yield of lysin in plant proteins range from 10.2 per cent in the globulin of the velvet bean to complete absence in zein of maize.

Table II. Distribution Of Nitrogen In Proteins *

TOTAL N = 100

NH3

N

Basic

Amino

Acids

N

Mono-

Amino

Acids

N

Humin

N

Total

N

Vegetable Proteins:

Conalbumin (egg white)......

7.51

25.82

65.11

1.61

16.11

Phaseolin (bean)............

10.74

24.50

62.85

1.79

16.20

Glycinin (pea)..............

12.09

22.63

64.58

.68

17.45

Legumelin (pea, bean).......

6.46

23.06

68.12

2.36

16.09

Leucosin (wheat)............

6.85

20.67

69.87

2.54

16.93

Glutenin (wheat)............

18.86

11.72

68.32

1.09

17.49

Gliadin (rye)...............

23.78

5.49

70.27

.79

17.66

Hordein (barley).................

23.30

4.47

69.96

1.33

17.21

Zein (maize)..............

18.41

3.03

77.56

.99

16.13

Globulin(wheat)...........

7.72

37.14

53.39

1.52

18.39

Globulin (coca nut)........

7.35

32.79

59.09

.75

18.48

Globulin (squash seed)......

6.91

32.25

59.64

1.18

18.51

Globulin (cotton seed).......

10.30

30.63

59.06

• • • •

18.64

Edestin (hemp seed)........

10.08

31.70

57.83

.64

18.64

Excelsin (para nut)........

8.87

31.47

59.94

.92

19.30

Corylin (hazel nut).........

11.57

30.26

56.31

.89

19.00

Amandin (almond).........

16.04

21.84

60.08

.89

19.00

Globulin (castor bean)......

10.45

30.08

58.66

.64

18.75

Corylin (walnut)..........

9.44

28.71

61.09

.79

18.84

Congluten (a) (lupine)......

11.84

29.05

58.00

1.00

17.90

Congluten (b) (lupine)......

14.55

28.17

56.56

.76

18.21

Legumin (pea)............

9.40

28.82

60.27

.94

17.97

Globulin (flaxseed).........

10.82

25.81

62.06

1.18

18.48

Vicilin (pea, bean)..........

10.40

27.76

60.60

1.22

17.11

Vignin (pea)..............

11.07

25.39

22.98

62.66

1.45

17.25

Globulin (sunflower seed)...

13.83

62.00

1.29

18.58

Stizolobin (Velvet bean).....

10.51

27.96

60.06

1.36

16.40

Arachin (Peanut)...........

11.10

27.13

60.50

1.20

18.28

Animal Proteins:

Vitellin (egg yolk)..........

7.67

28.56

62.41

1.35

1658

Casein (cow's milk).........

10.30

22.84

66.00

1.34

15.62

Ovalbumin (egg)...........

8.64

21.27

68.21

1.87

15.51

Chicken muscle...........

7.45

29.98

59.85

2.43

16.09

Halibut muscle............

6.70

30.18

60.73

2.37

16.40

Scallop muscle............

6.33

26.51

64.81

2.34

17.05

Beef muscle...............

5.50

27.32

64.52

2.65

16.18

* Compiled from the papers of T. B. Osborne and of C. O. Johns,

Table III. Content Of Arginin, Histidin And Lysin In Proteins *

Histidin

Arginin

Lysin

Vegetable Proteins:

Globulin (Buckwheat)....................

0.88

23.67

8.61

Globulin (Squash seed) ....

2.42

14.44

1.99

Excelsin (Para nut) ......

2.50

14.29

1.64

Edestin (Hemp seed) .....

2.19

14.17

1.65

Globulin (Cotton seed) .....

3.46

13.51

2.06

Stizolobin (Velvet bean) ....

3.81

14.13

10.02

Globulin (Castor bean) ....

2.74

13.19

1.54

Amandin (Almond) ......

1.87

12.16

0.72

Legumin (Pea)..........................

1.69

11.73

4.98

Legumin (Vetch)........................

2.94

11.06

3.70

Conglutin A (Lupine)....................

2.51

10.93

2.73

Vicilin (Pea)............................

2.17

8.91

5.40

Glycinin (Soy bean)......................

2.10

7.69

3.39

Vignin (Cow pea).......................

3.08

7.50

4.31

Glutelin (Maize)........................

3.00

7.06

2.93

Lecosin (Wheat)........................

2.83

5.94

2.75

Legumelin (Pea) ........

2.27

5.45

3.03

Legumelin(Soy bean).....................

2.04

5.35

4.91

Phaseolin (Kidney bean) ..........

2.62

4.87

4.58

Glutenin (Wheat) .......

1.76

4.72

1.92

Gliadin (Wheat) ........

0.58

3.16

1.33

Gliadin(Rye)...........................

0.39

2.22

• • •

Hordein (Barley) .......

1.28

2.16

• • •

Zein (Maize)...........................

0.82

1.35

0.00

Animal Proteins:

Ovovitellin (Egg yolk)....................

1.90

7.46

4.81

Beef muscle...........................

2.66

7.47

7.59

Scallop adductor musle...................

2.02

7.38

5.77

Chicken muscle........................

2.47

6.50

7.24

Halibut muscle.........................

2.55

6.34

7.45

Conalbumin (Egg white).................

2.17

5.07

6.43

Ovalbumin(Egg white)...................

1.71

4.91

3.76

Casein (Cow milk)......................

2.50

3.81

5.95

Lactalbumin ...........................

2.06

3.23

9.16

*This table is compiled from various sources, especially the papers of Osborne and of Johns.

A comparison of the relative amounts of these three digestion products in proteins of vegetable with those of animal origin reveals at once a remarkable fact. While the amount of histidin is of the same order in the two classes, arginin is found in many proteins of seeds in quantities greatly in excess of any of the proteins of animal tissues. The only vegetable proteins yet studied which exceed, in their content of lysin, the muscle proteins of animals, are those of the velvet bean and buckwheat (1).

Table IV. Per Cent Of Glutamic Acid Yielded By Proteins

Vegetable Proteins:

Gliadin (Wheat).................................

42.98 per cent.

Gliadin (Rye)....................................

37.80

Hordein (Barley) ................................

43.19

Zein (Maize) ...................................

26.17

Leucosin (Wheat).................................

5.72

Glutenin (Wheat)................................

23.40

Amandin (Almond)................................

23.14

Edestin (Hemp seed)...............................

14.00

Corylin (Hazel nut) ...............................

17.94

Phaseolin (Bean).................................

12.33

Vignin (Pea, bean)................................

16.30

Legumin (Vetch)..................................

16.48

Glycinin (Soy bean)...............................

19.46

Conglutin (Yellow lupine)..........................

30.05

Animal Proteins:

Casein (Cow milk) .............

10.77

Ovalbumin (Egg) .............

9.01

Conalbumin (Egg) .............

7.00

Vitellin (Egg yolk) .............

12.95

Serum albumin (Horse).............................

7.70

Serum globulin (Horse) ..........

8.50

Halibut muscle ...............

10.13

Chicken muscle ..............

16.48

Scallop muscle ...............

14.88

Dog tissues, entire body...........

14.00

Rabbit tissues, entire body.........

14.14

Hen tissues, entire body..................

12.02

*Compiled data from various sources, especially the papers of T. B. Osborne and E. Abderhalden.

It was the marked deficiency of most of the vegetable proteins in lysin in contrast to the animal proteins that led Osborne and Mendel and others to believe at one time that this amino-acid was frequently the limiting factor which determined the nutritive value of food proteins. The investigations relating to this phase of nutrition have been described in the preceding chapter.