ABSTRACT
Twenty-four analogues of D-glutamic acid were tested as substrates or inhibitors of the D-glutamate-adding enzyme from Escherichia coli. The best substrates were, in decreasing order of specific activity, D-erythro-4-methylglutamic acid, D-erythro-3-methylglutamic acid, DL-homocysteic acid, (+/-)-trans-1-amino-3-carboxy-cyclopentanecarboxylic acid and (+/-)-trans-1-amino-3-carboxy-cyclohexanecarboxylic acid. Among the different stereoisomers, only the D-erythro isomers for methylglutamic acids, and the trans isomers for the cyclic analogs, were substrates. Apart from the D-erythro-3- and 4-methylglutamic acids and DL-homocysteic acid, none of the examined compounds significantly inhibited the addition of radioactive D-glutamic acid to UDP-N-acetylmuramyl-L-alanine.
Subject(s)
Escherichia coli/enzymology , Glutamates/chemistry , Peptide Synthases/metabolism , Glutamic Acid , Peptide Synthases/antagonists & inhibitors , Peptidoglycan/biosynthesis , Stereoisomerism , Substrate SpecificityABSTRACT
The fluorescent diastereoisomeric adducts formed in a precolumn derivatization reaction of enantiomeric alpha-substituted amino acids with o-phthalaldehyde and N-acetyl-L-cysteine were separated by high-performance liquid chromatography on a conventional reversed-phase column. This method was particularly efficient for the complete analytical resolution of alpha-substituted glutamic acid analogues, such as 2-methylglutamic acid, and several cyclic analogues (1-amino-1,3-dicarboxycyclohexane, 1-amino-1,3-dicarboxy-2-cyclohexene and 1-amino-1,3-dicarboxycyclopentane). The order of elution from the column was correlated with the absolute configuration of the derivatives.
Subject(s)
Amino Acids/analysis , Glutamates/analysis , Chromatography, High Pressure Liquid , Stereoisomerism , o-PhthalaldehydeABSTRACT
Informations on the structural features implicated in the macrophage-dependent cytostatic activity of "lipid A" preparations were obtained by the use of 15 synthetic glycolipids. Four structural requirements were identified: the presence of a reducing glucosamine unit; the presence of a free hydroxyl group on amide-linked 3-hydroxytetradecanoic acids, and the absence of free hydroxyl groups at positions 3 and 6 of the glucosamine. The monosaccharide resembling the reducing unit of the "lipid A backbone," which fulfills these criteria, had the highest cytostatic activity, whereas the compound possessing the substitution pattern of the nonreducing moiety was inactive.
