The Path of Carbon in Photosynthesis: II. Amino Acids

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Abstract
The amino acid constituents of Chlorella pyrenoidosa and Scenedesmus D-3 were examined after exposure to C14O2 using the method of paper chromatography. Filter paper chromatograms were prepd. of whole cell extracts or amino acid mixtures obtained by absorption on cation exchange resins from the plant extracts. The chromatograms of the radioactive amino acids were scanned with a Geiger counter or radioauto-graphed. In Scenedesmus the following amino acids were found, listed in order of decreasing relative intensity of ninhydrin color on the chromatogram: glutamic acid, "unknown," phenylalanine, tyrosine, alpha-aminobutyric acid, lysine, beta-alanine, threonine, glycine, and proline. The radioactive amino acids photosynthesized in 30 sec. included aspartic acid chiefly and somewhat less alinine; other acids included asparagine, serine, beta-alanine, and phenylalanine. When the radioactive amino acids synthesized in the dark were separated the predominant product was aspartic acid with somewhat less alinine. The following acids were found in Chlorella extracts: glutamic acid, leucines, alanine, valine, glycine, and beta-alanine. Chlorella which photosynthesizes with C14O2 for 30 sec. forms chiefly aspartic acid with almost as much alanine. In all chromatograms the glutamic acid ninhydrin spot was strongly evident. In no case was radioactivity found coincident with this spot. Where glutamine was present there was no corresponding radioactivity. It appears that in both dark reduction of C14O2 and photosynthesis the same pattern of radioactivity in the amino acids occurs. The acids correspond to the 3-and 4-carbon amino acids.

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