Answer to Question #28647 in Inorganic Chemistry for Christian

Question

Would the hexapeptide Ala-Pro-Leu-Arg-Trp-Val give a positive Sakaguchi test? Would it give a positive Xanthoproteic test?

Answer 1

The Xanthoproteic test gives a positive result in thoseproteins with aminoacids carrying aromatic groups, especially in the presence of tyrosine. If the test is positive the proof is neutralized with an alkali, turning dark yellow. The yellow colour is due to Xanthoproteic acid which is formed due to nitration of certain amino acids, most common examples being tyrosine and tryptophan. In the hexapeptide Ala-Pro-Leu-Arg-Trp-Val tryptophan gives a positive Xanthoproteic test.
The Sakaguchi Test is used to test for a certain amino acid and proteins. The amino acid that is detected in this test is arginine. In the hexapeptide Ala-Pro-Leu-Arg-Trp-Val arginine gives a positive Sakaguchi Test.