The amino acid compositions of 7 marine green algal extracts were examined by means of an amino acid analyzer. Ulva pertusa was for the first time found to contain a dipeptide, L-arginyl-L-glutamine, in a large quantity. This peptide was detected also in Enteromorpha linza but not in the other five species. Glutamic acid and glutamine were relatively predominant in Codium fragile, C. adhaerens and Chlorodesmis comosa. In Caulerpa racemosa, the level of glycine was remarkably high. Glycine and proline were predominant in Cladophora densa.
Aminosulfonic acids in these algae were examined by paper chromatography. Taurine was detected in 4 species, D-cysteinolic acid in 3, N-monomethyltaurine in 2, and homotaurine in 1, respectively. Occurrence of homotaurine in Cladophora densa was also established.