151-41-7Relevant articles and documents
Nakamura
, p. 3013 (1975)
Hydrophobically modified water-soluble polymers and polyelectrolytes as micellar promotors in the Rh(I) catalyzed hydrogenation of an amino acid precursor in water
Fuhrmann, Hans,Grassert, Ingrid,Holzhueter, Gerd,Gruettner, Cordula,Oehme, Guenther
, p. 1675 - 1681 (2002)
Hydrophobically modified water-soluble polymers (HMWSP's) and hydrophobically modified polyelectrolytes (HMPE's, "polysoaps") of various compositions and different molecular weights have been prepared and used in the micellar promoted enantioselective hydrogenation of methyl (Z)-α-acetamidocinnamate with a chiral Rh(I) catalyst in aqueous medium. The efficiency of the micellar polymers in the catalytic reaction is greatly determined by their solubility (dispersibility) behavior and solubilization capacity for catalyst and substrate. The latters depends on the compactness of the polyamphiphiles as revealed by transmission electron microscopy (TEM) and light microscopy images. The highest catalytic performance was obtained with polymer-surfactant complexes prepared by micellar copolymerization with neutral or anionic tensides, regardless of the electrical charge of the hydrophobically modified polymer. In most cases a synergism between rate and enantioselectivity has been observed.
Influence of substrate structure on the catalytic efficiency of hydroxysteroid sulfotransferase STa in the sulfation of alcohols
Chen, Guangping,Banoglu, Erden,Duffel, Michael W.
, p. 67 - 74 (2007/10/03)
Sulfotransferase a (STa) is an isoform of hydroxysteroid (alcohol) sulfotransferase that catalyzes the formation of sulfuric acid esters from both endogenous and xenobiotic alcohols. Among its various functions in toxicology, STa is the major form of hepatic sulfotransferase in the rat that catalyzes the formation of genotoxic and carcinogenic sulfuric acid esters from hydroxymethyl polycyclic aromatic hydrocarbons. The goal of the present study was to elucidate fundamental quantitative relationships between substrate structure and catalytic activity of STa that would be applicable to these and other xenobiotics. We have modified previous procedures for purification of STa in order to obtain sufficient amounts of homogeneous enzyme for determination of k(cat)/K(m) values, a quantitative measure of catalytic efficiency. We determined the catalytic efficiency of STa with benzyl alcohol and eight benzylic alcohols that were substituted with n- alkyl groups (C(n)H(2n+1), where n = 1-8) in the para position, and the optimum value for k(cat)/K(m) in these reactions was obtained with n- pentylbenzyl alcohol. Correlations between logarithms of k(cat)/K(m) values and logarithms of partition coefficients revealed that hydrophobicity of the substrate was a major factor contributing to the catalytic efficiency of STa. Primary n-alkanols (C(n)H(2n+1)OH, where n = 3-16) exhibited an optimum k(cat)/K(m) for C9-C11 and a linear decrease in v(max) of the reaction for C3-C14; 15- and 16-carbon n-alkanols were not substrates for STa. These results indicated limits to the length of the extended carbon chain in substrates. Such limits may also apply to hydroxysteroids, since cholesterol was inactive as either substrate or inhibitor of STa. Furthermore, the importance of steric effects on the catalytic efficiency of STa was also evident with a series of linear, branched, and cyclic seven-carbon aliphatic alcohols. In conclusion, our results provide fundamental quantitative relationships between substrate structure and catalytic efficiency that yield insight into the specificity of STa for both endogenous and xenobiotic alcohols.
