Active site structure and general

Active Site Structure and General Reaction Catalyzed... 

In the crystal structures, the inhibitors coordinate to the active site zinc and make a series of hydrogen bonds via their hydroxamic acid moiety. The hydroxamic acids are linked by a flexible spacer with bulky cap groups. The aromatic or aliphatic spacer participates in van der Waals interactions throughout the long charmel, whereas the terminal part of the inhibitor interacts with residues at the rim of HDAC. In general, the binding mode of the cocrystallized inhibitors TSA and SAHA is conserved among the different species and subtypes [35]. 

Figure 2 Structure of DNA polymerases, (a) The structure of Pol I represents the general right-hand shape of all DNA polymerases (PDB ID IQSY). Subdomains and the 3 -5 exonuclease domain are indicated, (b) The chain topology in the palm domain of DNA polymerases indicates their evolutionary heritage. Left The A, B, and Y family have four antiparallel sheets supported by two a helices. The three aspartic residues that chelate the metal ions are indicated by dots. Right The C-famiiy and X-family DNA polymerases contain a set of paraiiei strands on which the acidic residues that chelate metal are oriented differently from the A-, B-, and Y-family DNA polymerases, (c) During misincorporation of an incorrect nucleotide, the DNA must leave the polymerase active site (left) and enter the 3 -5 exonuclease active site (right). This action requires the melting of three to four base pairs.

By virtue of their complex macromolecular structure, including a highly defined active site, enzymatic transformations generally proceed with a high degree of chemical selectivity and stereospecificity. Reactions are typically conducted under mild conditions of temperature, pressure, and pH, thus minimizing losses caused by unwanted side reactions or partial racemization. The use of extremo-philes or cross-linked enzymes such as CLECs... 

Dendrimers are a class of macromolecules with highly branched and well-defined structures, and have recently attracted much attention as soluble supports for (chiral) catalyst immobilization [55-65]. As stated above, the catalysts anchored onto or into insoluble supports often possess an uneven catalytic site distribution and partly unknown structures, and generally suffer from diminished activity due to the mass transfer hmitations. Dendrimers, on the other hand, allow for the precise construction of catalyst structures with uniformly distributed catalytic... 

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