Sakaguchi Test
(Detection of Arginine)
The Sakaguchi test is a chemical test used for detecting the presence of arginine in proteins. It is named after the Japanese Food Scientist and Organic Chemist, Shoyo Sakaguchi (1900–1995) who described the test in 1925.
Principle:
Sakaguchi test is given by guanidinium compounds. The only amino acid containing the guanidine group is arginine. Therefore this test is specific for identification of arginine. Arginine reacts with α-naphthol in presence of an oxidizing agent such as bromine water or sodium hypochlorite to give a red coloured product. The other guanidine containing non-amino acid compounds also give this reaction.
Reaction:
Reagents:
- Test solutions:
- Amino acids: 0.1 % solution of amino acids like glycine, arginine, lysine, tyrosine, etc.
- Protein solution: egg albumin in distilled water (around 10%)
- Guanidines: 0.1 % solutions of glycocyamine, methyl guanidine, and creatine.
- NaOH: 40% (w/v).
- α-Naphthol: 1% in alcohol.
- Bromine water: Add a few drops of bromine to 100 ml water and shake. This should be done in a fume chamber. (Caution: Bromine can cause severe burns). Or use 10% sodium hypochlorite solution
Procedure:
- Mix 1 ml of NaOH with 3 ml of the amino acid or test solution
- Then add 2 drops of α-naphthol.
- Mix thoroughly and add 4 to 5 drops of bromine water or add 1 to 2 drops of 10% sodium hypochlorite.
- Watch for the formation of red colour.
Result Interpretation:
Positive test: Formation of red colour indicate presence of arginine or a guaniginium compound.
Negative test: No formation of red colour indicate absence of arginine or a guaniginium compound.
References:
- Sawhney S.K (2016), Introductory Practical Biochemistry, Eleventh reprint, Narosa Publishing House Pvt. Ltd, 22 Delhi Medical Association Road, Daryaganj, New Delhi-110002.
- https://en.wikipedia.org/wiki/Sakaguchi_test
- https://www.onlinebiologynotes.com/sakaguchi-test-objective-principle-reagents-procedure-and-result/
- https://www.oxfordreference.com/view/10.1093/oi/authority.20110803100437376
- https://www.coursehero.com/file/33805624/Sakaguchi-Testpptx/
- https://www.jbc.org/content/159/1/185.full.pdf
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