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The Sakaguchi test is a chemical test used to detect 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. [1] The Sakaguchi reagent used in the test consists of 1-Naphthol and a drop of sodium hypobromite.
The Sakaguchi test detects the presence of arginine in protein; The Hopkins–Cole reaction tests for the presence of tryptophan in proteins; The nitroprusside reaction tests for the presence of free thiol groups of cysteine in proteins; The Sullivan reaction tests for the presence of cysteine and cystine in proteins
In enzymology, an arginine racemase (EC 5.1.1.9) is an enzyme that catalyzes the chemical reaction L-arginine ⇌ {\displaystyle \rightleftharpoons } D-arginine Hence, this enzyme has one substrate , L- arginine , and one product , D- arginine .
Arginine is the amino acid with the formula (H 2 N)(HN)CN(H)(CH 2) 3 CH(NH 2)CO 2 H. The molecule features a guanidino group appended to a standard amino acid framework. At physiological pH, the carboxylic acid is deprotonated (−CO 2 −) and both the amino and guanidino groups are protonated, resulting in a cation.
The base initiates the reaction by deprotonating the carbon adjacent to the arginine, or leaving group. Recent mutagenic studies of ASL homologues have shown that Histidine 162 or Threonine 161 of ASL is responsible for the proton abstraction of the Cβ, either directly or indirectly through a water molecule. [ 6 ]
Some cells synthesize argininosuccinic acid from citrulline and aspartic acid and use it as a precursor for arginine in the urea cycle (or citrulline-NO cycle), releasing fumarate as a by-product to enter the TCA cycle. The enzyme that catalyzes the reaction is argininosuccinate synthetase. [3] [4]
The characteristic color of a positive biuret test. In chemistry, the biuret test (IPA: / ˌ b aɪ j ə ˈ r ɛ t /, / ˈ b aɪ j ə ˌ r ɛ t / [1]), also known as Piotrowski's test, is a chemical test used for detecting the presence of at least two peptide bonds in a molecule.
Arginase (EC 3.5.3.1, arginine amidinase, canavanase, L-arginase, arginine transamidinase) is a manganese-containing enzyme. The reaction catalyzed by this enzyme is: arginine + H 2 O → ornithine + urea. It is the final enzyme of the urea cycle. It is ubiquitous to all domains of life.