Catalytically perfect enzyme or kineticall perfect enzyme is an enzyme that catalyzes so efficiently, that almost every time enzyme meets its substrate, the reaction occurs. k_cat/K_m factor of such enzyme is of order 10⁸ to 10⁹ M^-1 s^-1. Such reaction is only limited by substrate diffusion rate. Ribbon diagram of the enzyme TIM. TIM is catalytically perfect, meaning its conversion rate is limited, or nearly limited to its substrate diffusion rate. ... A catalyst (Greek: καταλύτης, catalytÄ“s) is a substance that accelerates the rate (speed) or ease of a chemical reaction (see also catalysis) without itself being changed at the end of the chemical reaction . ... The word substrate can mean the following: In biochemistry, a substrate is a molecule which is acted upon by an enzyme. ...

Some catalytically perfect enzymes are triose-phosphate isomerase, carbonic anhydrase, acetylcholinesterase, catalase, fumarase, ß-lactamase, and superoxide dismutase. Ribbon diagram of the TIM enzyme. ... Carbonic anhydrase (carbonate dehydratase) is a family of metalloenzymes (enzymes that contain one or more metal atoms as a functional component of the enzyme) that catalyze the rapid interconversion of carbon dioxide and water into carbonic acid, protons, and bicarbonate ions. ... In biochemistry, cholinesterase is a term which refers to one of the two enzymes (EC 3. ... Catalase Catalase (human erythrocyte catalase: PDB 1DGF, EC 1. ... Fumarase is an enzyme involved in the Krebs Cycle that catalyzes the hydration (addition of H2O across a double bond) of Fumarate to L-malate (the natural optical isomer of a protein as apposed to the d isomer) Fumarase Deficiency In humans, Fumarase Deficiency is an enzyme irregularity that causes... Beta-lactamase is a type of enzyme (EC 3. ... Superoxide dismutase The enzyme superoxide dismutase (SOD, EC 1. ...

Some enzymes operate with kinetics which are faster than diffusion rates, which would seem to be impossible. Several mechanisms have been invoked to explain this phenomenon. Some proteins are believed to accelerate catalysis by drawing their substrate in and preorienting them by using dipolar electric fields. Some invoke a quantum-mechanical tunneling explanation whereby a proton or an electron can tunnel through activation barriers, although for protons tunneling remains somewhat controversial. ^[1][2] Quantum tunneling is the quantum-mechanical effect of transitioning through a classically-forbidden energy state. ...

References

1. ^ Mireia Garcia-Viloca,1 Jiali Gao,1 Martin Karplus,2* Donald G. Truhlar Science 9 January 2004:Vol. 303. no. 5655, pp. 186 - 195
2. ^ Olsson MH, Siegbahn PE, Warshel A. J Am Chem Soc. 2004 Mar 10;126(9):2820-8.