Enzymatic Mechanisms General Acid-Base Catalysis

Enzymatic Mechanisms General Acid-Base Catalysis... 

Common organic reaction mechanisms, such as nucleophilic substitution and general acid-base catalysis, are known to play roles in enzymatic catalysis. 

The impact of nucleophilic and electrophilic groups of the active center on the substrate at the contact area in the enzyme-substrate complex (the effect of synchronous intramolecular catalysis). The polyfunctional catalysis involves a great many processes push-pull mechanisms, processes involving a relay charge transfer, as well as a general acid-base catalysis. Presumably, the enzyme in the initial state of the enzymatic reaction already contains structural elements of the transition state and in this case the reaction must be thermodynamically more advantageous. 

Knowing the values of individual histidine residues in an enzyme can be important for understanding the mechanism by which an enzyme carries out its catalytic function. The imidazole groups in the side chains of histidine residues in proteins generally have pK values in the range of 5-8. Thus, histidine residues are especially well equipped to participate in the many catalytic processes of enzymatic reactions that use general acid-base catalysis. 

Several broad themes recur frequently in enzymatic reaction mechanisms. Among the most important of these are (1) proximity effects, (2) general-acid and general-base catalysis, (3) electrostatic effects, (4) nucleophilic or electro-philic catalysis by enzymatic functional groups, and... 

Biochemical ion-transfer reactions, and especially proton-transfer reactions, are enormously important for life. They are used in catalysis of acid-base reactions and enzymatic catalysis, or to establish concentration gradients in living cells. Many biomolecules exhibit proton-transport chaimels through which protons may be transported. These ehannels are designed by the molecule s structure, and generally filled with a small amount of water molecules. The water in this eonfined system is used to transport the proton via a Grotthuss-type mechanism. 

---