Deficiency

The unique sequence of amino acids in proteins demands that all amino acids, whether essential or non-essential, be present at the sites of protein synthesis. In the event of any deficit, the utilization of the remaining amino acids will be prejudiced and protein synthesis and other physiological processes will be impaired. Thus, it might be assumed that dietary deficiencies of individual essential amino acids would lack distinctive features. However, the published evidence indicates unique effects of particular amino acids. This evidence has been derived primarily from studies in which the amino acid in question has been omitted altogether. In addition, recent investigations on determination of maintenance requirements have yielded valuable data on the effects of graduated degrees of deficiency of particular essential amino acids.

Table 1.4. Efficacy of isomers and analogues of amino acids. Values represent growth efficacy as a percentage of that of the L-isomer. (Adapted from Baker, 1994.)

Amino acid

Chick

Rat

Mouse

Dog

Pig

□-lysine

0

0

0

D-threonine

0

0

0

-

-

□-tryptophan

20

100

30

35

80

□-methionine

90

90

75

100

100

□L-methionine

95

95

88

100

100

□L-OH-methionine

80

-

70

-

100

Keto-methionine

90

-

-

-

-

W-acetyl-L-methionine

100

100

90

100

-

D-arginine

0

0

-

-

-

D-histidine

10

0

10

-

-

D-leucine

100

50

15

-

-

D-valine

70

15

5

-

-

□-isoleucine

0

-

-

-

-

□-phenylalanine

75

70

-

-

-

L-O H -p henylalan i ne

70

50

-

-

-

Keto-phenylalanine

85

65

-

-

-

D-tyrosine

100

100

-

-

-

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