The steady-state kinetics of isotope exchange for one substrate–one product enzymic reactions

Steady-state kinetic equations for isotope exchange are derived for a number of one substrate-one product enzymic mechanisms in which two molecules of substrate or product can be combined with an enzyme molecule at the one time (e.g. allosteric mechanisms). The usual assumption, that the radioactive material is distributed among the substrate and product components according to a first-order law, is not valid. One can recognize whether isotope-exchange kinetics of an enzyme reaction follows first-order behaviour by using various initial concentrations of the labelled substance added to a mixture.     

The application of product inhibition studies to one substrate–one product enzymic reactions

A graphical procedure is presented for distinguishing between possible mechanisms of one substrate-one product enzymic reactions.     

Structural characterization of β-ketoacyl ACP synthase I bound to platencin and fragment screening molecules at two substrate binding sites

The bacterial fatty acid pathway is essential for membrane synthesis and a range of other metabolic and cellular functions. The β-ketoacyl-ACP synthases carry out the initial elongation reaction of this pathway, utilizing acetyl-CoA as a primer to elongate malonyl-ACP by two carbons, and subsequent elongation of the fatty acyl-ACP substrate by two carbons. Here we describe the structures of the β-ketoacyl-ACP synthase I from Brucella melitensis in complex with platencin, 7-hydroxycoumarin, and (5-thiophen-2-ylisoxazol-3-yl)methanol. The enzyme is a dimer and based on structural and sequence conservation, harbors the same active site configuration as other β-ketoacyl-ACP synthases. The platencin binding site overlaps with the fatty acyl compound supplied by ACP, while 7-hydroxyl-coumarin and (5-thiophen-2-ylisoxazol-3-yl)methanol bind at the secondary fatty acyl binding site. These high-resolution structures, ranging between 1.25 and 1.70 å resolution, provide a basis for in silico inhibitor screening and optimization, and can aid in rational drug design by revealing the high-resolution binding interfaces of molecules at the malonyl-ACP and acyl-ACP active sites.