Amino Acids in Blood and Organs

About 5.5—8 mg-% amino acid nitrogen is found in the plasma of a fasting human. The concentrations he between 0.03 mg- % for aspartic acid and 8.3 mg-% for glutamine. Oral administration of individual amino acids leads to increases of these amino acids in peripheral blood. 

The free amino acids in plasma have been separated by Opienska-Blauth [114] on cellulose MN-300 layers, using the solvents butanol-acetic acid-water (60+ 15+ 15) and phenol-water (75+ 25). 14 nin-hydrin-positive spots were isolated from 20 [A plasma. Pataki and Keller [117] have been able to detect 21 ether- and water-soluble dinitro-phenyl-amino acids in 60 [xl serum no histidine was, however, present. 

With the help of one- and two-dimensional TLC on sihca gel G, Dimillier and Trout [29] have observed increases in concentration of histidine, prohne, hydroxyproline, serine, threonine, aspartic acid, glutamic acid and tryptophan in blood during extracorporal circulation this increase was proportional to the duration of the extracorporal circulation. Through TLC on sihca gel layers with the solvent n-butanol-acetic acid-water (60 + 15 + 15), V. Euler and co-workers (40) have been able to isolate from the tumour serum of the rat, after precipitation of proteins with methanol, a substance of hJ /-value of 23 which was present at much lower concentration in the normal serum. By chromatographing again in two different solvents it could be identified as glycine. 

Wernze and Fujn [187] have employed TLC on ceUulose layers for quantitative determination of the valine hberated by enzymatic hydrolysis as a measure of the angiotensinase activity in plasma and renal tissue. The data were stated to be reproducible. 

The use of labelled substances is an indispensable technique in research on metabohc routes. Drawert and co-workers [33] have added C-labelled glutamic acid to fermentation mixtures and found that the dinitrophenyl derivatives of glutamic acid, alanine, aspartic acid, prohne and glycine, separated by TLC, were radioactive. 

---