Catalytic amino acid residues

Catalytic amino-acid residues found in enzymes... 

Isaksson, R. The catalytic amino acid residues in the active site of cellobiohydrolase 1 are involved in chiral recognition,... 

Figure 24 The proposed roles of key catalytic amino acid residues in (a) adenylation and/or (b) thioesterification during 4-chlorobenzoate CoA (CBL) catalysis.

Papain, EC 3.4.22.2, the archetype of cysteine peptidases. It was isolated from the latex of the tropical papaya fruit (Carica papaya). Papain is a single-chain protein (212 aa 23 kDa) containing three disulfide bonds and a known three-dimensional structure with 1.65 A resolution The catalytic amino acid residues have been identified as Cys, His and Asn, whereas Gln helps to stabilize the oxyanion hole. Papain has a fairly broad specificity [J. R. Kimmel, E. L. Smith, J. Biol. Chem. 1954, 207, 515 A. C. Storer, R. Menard, Methods Enzymol. 1994, 244, 486]. 

Responsibility of Catalytic Amino Acid Residues of the Enzyme. 107... 

In order to further verify the involvement of catalytic amino acid residues in enzyme-catalyzed ring-opening polymerization, catalytic amino acids of the catalytic domain of the PHB depolymerase were replaced and evaluated for their polymerization activities. PHB depolymerases have structures that consist of a catalytic domain, a putative linker region, and a substrate binding domain (SBD). Three strictly conserved amino acids, serine, aspartate, and histidine, constitute the catalytic triad at the active center of the catalytic domain. The conserved serine is part of the so-called lipase-box... 

Why are enzymes macromolecules The reason is that the active center must be of a defined or highly ordered geometry if it is to contain all the binding and catalytic amino acid residues in a correct alignment for optimal catalysis. This imposes a heavy entropy demand upon the system which can be compensated for at the expense of another already ordered region of the biopolymer (58). 

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