Subunit Interactions in Enzyme Catalysis. Kinetic Models for One-Substrate Polymeric Enzymes

Substrate catalysis enhances single-enzyme diffusion.

We show that diffusion of single urease enzyme molecules increases in the presence of urea in a concentration-dependent manner and calculate the force responsible for this increase. Urease diffusion measured using fluorescence correlation spectroscopy increased by 16-28% over buffer controls at urea concentrations ranging from 0.001 to 1 M. This increase was significantly attenuated when urease...

Substrate recognition and catalysis by flap endonucleases and related enzymes.

FENs (flap endonucleases) and related FEN-like enzymes [EXO-1 (exonuclease-1), GEN-1 (gap endonuclease 1) and XPG (xeroderma pigmentosum complementation group G)] are a family of bivalent-metal-ion-dependent nucleases that catalyse structure-specific hydrolysis of DNA duplex-containing nucleic acid structures during DNA replication, repair and recombination. In the case of FENs, the ability to ...

Quantum Catalysis in Enzymes

Enzyme-catalysed reactions span a wide range of reaction types and mechanisms. In many cases the rate-determining step is the transfer of a proton, hydride ion, or hydrogen atom; such reactions are almost always dominated by quantummechanical tunnelling. The effective barrier for tunnelling is highly dependent on the evolution of zero-point energy along the reaction path, and zero-point energy ...

Kinetic evidence for a substrate-induced fit in phosphonoacetaldehyde hydrolase catalysis.

Phosphonoacetaldehyde hydrolase (phosphonatase) from Bacillus cereus catalyzes hydrolytic P-C bond cleavage of phosphonoacetaldehyde (Pald) via a Schiff base intermediate formed with Lys53. A single turnover requires binding of Pald to the active site of the core domain, closure of the cap domain containing the Lys53 over the core domain, and dissociation of the products following catalysis. Th...

Kinetic Isotope Effects as Probes for Hydrogen Tunneling in Enzyme Catalysis