PLANTS
VERSUS ANIMALS IN THE DINING HALL(1)
Case Study in Amino Acid Metabolism
Page 3 -
Where did it go and how did it get there?
Maura found the results of another experiment interesting, though again she didn't like the idea that animals had to be killed in the experiment. Instead of using labeled sucrose as in Table 1, 15N-glutamate or other 15N-labeled amino acids were injected into adult albino rats maintained ad libitum on a diet of bread, milk, oats, and carrots. Two rats were used for each 15N-labeled amino acid tested (100mg/100g rat weight). After eight hours, the rats were killed and the total protein isolated from their livers. After hydrolysis and chromatography, the 15N-content of various amino acids was determined by mass spectrometry. Table 2 that follows summarizes some of the results of that study (Aqvist, 1951).
Before you go on, what factors will influence the distribution
of 15N from a source
amino acid into other amino acids?
Table 3. Distribution of 15N
among the amino acids of liver proteins 8 hours after intravenous injection
of various amino acid sources of 15N.
Values are normalized to the 15N
content of the source amino acid (100) incorporated into protein.
[Aqvist,
S. E. G. (1951) "Metabolic Interrelationships among Amino Acids Studied
with Isotopic Nitrogen." Acta Chem. Scand. 5, 1046-1064]
|
|
|||||||||||||||
| 15N-enriched Amino Acid | Glu | Asp | Ala | Pro | Thr | Ser | Gly | Leu | Ile | Val | Phe | Tyr | Arg | Lys | His |
| Glutamate |
100
|
50
|
74
|
12
|
3
|
46
|
19
|
31
|
nd
|
20
|
14
|
20
|
34
|
4
|
2
|
| Aspartate |
186
|
100
|
125
|
29
|
2
|
40
|
38
|
49
|
111
|
nd
|
26
|
38
|
60
|
15
|
25
|
| Alanine |
77
|
44
|
100
|
16
|
<1
|
23
|
21
|
38
|
40
|
29
|
9
|
10
|
33
|
4
|
3
|
| Proline |
23
|
14
|
18
|
100
|
1
|
5
|
3
|
4
|
5
|
5
|
1
|
2
|
11
|
2
|
<1
|
| Threonine(1) |
6
|
5
|
5
|
2
|
100
|
20
|
14
|
1
|
2
|
4
|
2
|
5
|
5
|
1
|
<1
|
| Serine |
9
|
9
|
12
|
2
|
14
|
100
|
50
|
3
|
2
|
2
|
2
|
6
|
9
|
1
|
1
|
| Glycine |
19
|
12
|
16
|
1
|
0
|
88
|
100
|
nd
|
nd
|
nd
|
3
|
nd
|
16
|
<1
|
2
|
| Leucine |
30
|
15
|
25
|
nd
|
<1
|
7
|
7
|
100
|
25
|
12
|
3
|
7
|
11
|
0
|
<1
|
| Isoleucine |
28
|
14
|
23
|
11
|
<1
|
9
|
8
|
34
|
100
|
15
|
8
|
12
|
10
|
4
|
3
|
| Valine |
34
|
19
|
29
|
7
|
0
|
12
|
10
|
46
|
41
|
100
|
5
|
6
|
14
|
1
|
2
|
| Phenylalanine |
24
|
12
|
18
|
2
|
<1
|
3
|
2
|
3
|
5
|
3
|
100
|
74
|
10
|
7
|
2
|
| Tyrosine(2) |
23
|
13
|
16
|
3
|
<1
|
4
|
4
|
4
|
5
|
4
|
44
|
100
|
9
|
1
|
1
|
| Arginine(3) |
34
|
23
|
20
|
18
|
2
|
6
|
1
|
nd
|
nd
|
nd
|
11
|
10
|
100
|
13
|
5
|
| Lysine3 |
23
|
19
|
12
|
5
|
3
|
8
|
3
|
nd
|
nd
|
nd
|
6
|
nd
|
9
|
100
|
4
|
| Histidine3 |
28
|
25
|
30
|
6
|
2
|
8
|
10
|
nd
|
nd
|
nd
|
9
|
nd
|
24
|
6
|
100
|
List at least five patterns you observe in the data.
Considering what is now known about amino acid metabolism (see your textbook), qualitatively analyze and interpret the data. If present, please identify any discrepancies or possible errors in the data.
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2. Administered by a stomach tube. Animals killed after 12 hours.
3. 15N excess significantly less than
for other administered amino acids.