1944-42-9Relevant academic research and scientific papers
Kinetics and mechanism of oxidation of α-amino acids by Fremy's radical in aqueous borate buffer medium
Kawle, Baloji,Thirupathi Rao,Adinarayana
, p. 667 - 670 (2007/10/03)
Oxidation of α-amino acids viz., glycine, alanine, phenylalanine, valine, aspartic acid, serine and threonine by Fremy's radical (potassium nitrosodisulphonate, PNDS) in aqueous-borate buffer medium at pH 10.0 shows first order dependence each on [PNDS] and [α-amino acid]. Under the experimental conditions PNDS has been found to be quite stable. However, the little'self decomposition of PNDS found on standing for longer period has been prevented by the addition of sulphamate ion. Increase in ionic strength of the medium has no effect on the rate of oxidation. The mechanism proposed involves direct attack of PNDS on α-amino acid to give an α-amino acid radical. PNDS being a very good radical trap, efficiently reacts with α-amino acid radicals to give α-keto acid via easily hydrolysable α-imino acid. The order of reactivity has been found to be phenylalanine > alanine > serine > glycine > valine > threonine > aspartic acid.
Structure-Activity Studies with the αβ-Dihydroxyacid Dehydratase of Salmonella typhimurium
Armstrong, Frank B.,Lipscomb, Elizabeth L.,Crout, David H. G.,Morgan, Phillip J.
, p. 691 - 696 (2007/10/02)
(2RS,3RS)- and (2RS,3SR)-2,3-Dihydroxybutanoic acids, (2R,3R)-2,3-dihydroxy-3-methylpentanoic acid, (2RS)-2-ethyl-2,3-dihydroxypentanoic acid, (2RS,3RS)- and (2RS,3SR)-2,3-dihydroxy-3-methylhexanoic acids, and (2RS,3RS)- and (2RS,3SR)-2,3-dihydroxy-3-methylheptanoic acids were synthesised.These acids, as well as (RS)-2,3-dihydroxy-3-methylbutanoic acid and (RS)-glyceric acid were tested as substrates for the αβ-dihydroxyacid dehydratase of the isoleucine-valine biosynthetic pathway of Salmonella typhimurium.For acids having a propyl group at C-3, the activities were greatly reduced compared with those obtained for the natural substrates (2R,3R)-2,3-dihydroxy-3-methylpentanoic acid and (R)-2,3-dihydroxy-3-methylbutanoic acid .For acids having an n-butyl substituent at C-3, the activities were close to zero. (2RS,3SR)-2,3-Dihydroxybutanoic acid (threo isomer) underwent dehydration at a rate comparable with that of (2R,3R)-DHI, the natural substrate in the isoleucine pathway, whereas the (2RS,3RS)-acid (erythro-isomer) had much lower activity and (RS)-glyceric acid had even less activity.These results illustrate differences in the alkyl group requirements with respect to the areas of the binding site of the enzyme that accomodate the C-3 substituents.They also demonstrate the size limits of the alkyl groups that can be accomodated in substrate analogues.
