Active sites hydrogenation

Eq. 1 AGbind, free energy of binding Nw, number of active site hydrogen bonds formed between substrate and human CYP2A6 log P, logarithm of the octanol/water partition coefficient. 

Ido, E., Kezdy, F.J., Han, H., and Tang, J. (1991) Kinetic studies of human immunodeficiency vims type I protease and its active-site hydrogen bond mutant A28S.T. Biol. Chem., 226, 24359-24366. 

The alcohol dehydrogenases were already described in Chapter 3. These enzymes are cofactor dependent and in the active site hydrogen transfer takes place from NADH or NADPH. In the reverse way they can, however, be applied for the oxidation of alcohols in some cases (see below). Oxidases are very appealing for biocatalytic purposes, because they use oxygen as the only oxidant without the need for a cofactor. Oxidases usually have flavins (glucose oxidase, alcohol oxidase) or copper (examples galactose oxidase, laccase and tyrosinase) in the active site [18]. The mechanism for glucose oxidase (GOD) is denoted in... 

Atkins, W. M., and Sligar, S. G., 1988, The roles of active site hydrogen bonding in cytochrome P450 cam as revealed by site-directed mutagenesis, J. Biol. Chem., 263 18842n18849. 

Low DW, Hill MG. Backbone-engineered high-potential iron proteins effects of active-site hydrogen bonding on reduction potential. J. Am Chem. Soc. 2000 122 11039-11040. 

In the extreme, the proton affinities of the enolate anion and active site donor could be the same, depending on the identities of the substrate and active site hydrogen bond donor. 

Mn-SOD protein. Since the compositions of the active site hydrogen bonding networks are the same, increased stabilization of OH at one end of the H bond network in Mn-SOD (depression of the pK of coordinated solvent) should come at the cost of less H bond donation to Tyr34, consistent with the much higher pK of Tyr34 in Mn -SOD than in Fe -SOD. Thus, the different tuning is intimately related to the different active site pKs. 

Studies of chemisorption of hydrogen, water, carbon monoxide, and carbon dioxide alone and in sequence on a Cu-Cr-Zn low temperature methanol synthesis catalyst show that the catalyst surface contains two different types of active sites. Hydrogen and water are chemisorbed in competition on one type, carbon monoxide and carbon dioxide on the other. The results for Cu-Zn-Al catalysts follow the same pattern. 

E. Ido, H. P. Han, F. J. Kezdy, and J. Tang,/. Biol. Chem., 266,24349 (1991). Kinetic Studies of Human Immunodeficiency Virus Type 1 Protease and Its Active-Site Hydrogen Bond Mutant A28S. 

---