title: Studies on the enzymes involved in the biosynthesis of cyclo-tris (N-2,3-dihydroxybenzoyl-L-seryl) in Escherichia coli: kinetic properties of the L-serine-activating enzyme.
abstract: Some kinetic properties of the formation of a thioester-bound l-seryl-enzyme intermediate are described. The rate constant of formation is 3.12 x 10(2) M(-1) s(-1) and the rate constant for spontaneous breakdown is 2.47 x 10(-3) s(-1). These constants yield a value of log K = 5.10 for the overall equilibrium constant which agrees favorably with a value of 5.20 calculated from equilibrium binding data. E(1).serine formation requires a thiol group which is extremely reactive to N-ethylmaleimide; the second-order rate constant for enzyme inactivation by this reagent is 77.1 M(-1) s(-1) at pH 6.6 and 0 C. Excess l-serine does not protect the enzyme against inactivation. In addition to an adenosine triphosphate-[(32)P]-inorganic pyrophosphate exchange, the enzyme also catalyzes an l-serine-dependent adenosine triphosphate-[(3)H]adenosine monophosphate exchange in accordance with the scheme proposed for the activation of serine.
mesh_terms: D000249:Adenosine Monophosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000409:Alanine / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D004355:Drug Stability; D004790:Enzyme Induction; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology*; D005033:Ethylmaleimide / Q000494:pharmacology; D005998:Glycine / Q000378:metabolism; D006096:Gramicidin / Q000494:pharmacology; D006639:Histidine / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007930:Leucine / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism; D010761:Phosphorus Radioisotopes; D011392:Proline / Q000378:metabolism; D012694:Serine / Q000378:metabolism*; D013912:Threonine / Q000378:metabolism; D013997:Time Factors; D014316:Tritium; D014443:Tyrosine / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D010710:Phosphates; D010761:Phosphorus Radioisotopes; D014316:Tritium; D006096:Gramicidin; D013912:Threonine; D000249:Adenosine Monophosphate; D014443:Tyrosine; D012694:Serine; D006639:Histidine; D000255:Adenosine Triphosphate; D011392:Proline; D007930:Leucine; D008239:Lysine; D005033:Ethylmaleimide; D000409:Alanine; D005998:Glycine