Cleland’s nomenclature

Enzymes are biocatalysts, as such they facilitate rates of biochemical reactions. Some of the important characteristics of enzymes are summarized. Enzyme kinetics is a detailed stepwise study of enzyme catalysis as affected by enzyme concentration, substrate concentrations, and environmental factors such as temperature, pH, and so on. Two general approaches to treat initial rate enzyme kinetics, quasi-equilibrium and steady-state, are discussed. Cleland s nomenclature is presented. Computer search for enzyme data via the Internet and analysis of kinetic data with Leonora are described. 

Common practice Cleland s nomenclature Equations Figures... 

In Cleland s nomenclature, substrates are designated by the letters A, B, and C in the order which they add to the enzyme, and products by the letters P, Q, and R in order in which they leave the enz5mie. There are two types of enzyme forms those which are stable on the timescale of several minutes or more, and those which are basically enzyme-reactant complexes and wiU dissociate on a timescale of seconds or milliseconds. Stable enzyme forms are designated E, F, and G. The stable forms can usually be isolated by chemical methods and latter shown to transfer the group they are carrying to one of the reactants. 

In Cleland s nomenclature, the concentrations of two substrates are indicated as A and B, and in Dalziel s nomenclature as Si and Sa- In Cleland s nomenclature, the maximal velocity is Vi, the MichaeUs constants and K, and the inhibition constant KjA-In DaMel s nomenclature, kinetic factors have the following meaning ... 

The rate Eq. (9.8) is written in Cleland s nomenclature, with one inhibition constant defined for each reactant in the mechanism (KIa. iq This rate equation was dended in Chapter 4 with the aid of the King-Altman method (Eq. (4.39)). 

Selectivity is an intrinsic properly of enzymatic catalysis. [3] Following the nomenclature proposed by Cleland [24, 25], the pseudo second-order rate constant for the reaction of a substrate with an enzyme, kml/KM, is known as the specificity constant, ksp. [26] To express the relative rates of competing enzymatic reactions, involving any type of substrates, the ratio of the specificity constants appears to be the parameter of choice [3]. Since the authoritative proposition by Sih and coworkers [27], the ratio of specificity constants for the catalytic conversion of enantiomeric substrates, R and S, is commonly known as the enantiomeric ratio or E -value (Equation 1) ... 

---