The remarkably high enantioselectivity (
k,
La, obsd/
kDa, obsd = 1000) was attained for the hydrolysis of amino acid esters (
N-dodecanoyl-D (L) -phenylalanine
p-nitrophenyl ester; C
12-D (L) -Phe-PNP) catalyzed by the active tripeptide (
N- (benzyloxycarbonyl) -L-phenylalanyl-L-histidyl-L-leucine; Z-Phe-His-Leu) in the coaggregate systems composed of 41 mol% hexadecyltrimethylammonium bromide (CTAB) and 59 mol% ditetradecyldimethylammonium bromide (2 C
14Br) at the specific ionic strength (μ =0.02). With respect to the temperature dependence of hydrolysis in the coaggregate systems composed of native lipid (L-α-dipalmitoylphosphatidylcholine; DPPC) and nonionic surfactant (α- [4- (1, 1, 3, 3- tetramethylbutyl) phenyl] -ω-hydroxydecakis (oxyethylene); Triton X-100), the enantioselectivity was maximized at the phase transition temperature (
Te) and the hydrophobic microenvironment of coaggregates could be evaluated on the basis of isokinetic temperature (β). On the other hand, in the stereoselective hydrolysis of dipeptide esters as mediated by cyclodextrins (CyD), a high diastereoselectivity (
kDL2/
kLL2 =46) and preferential binding property (
KDLb/
KLLb= 2.4) were observed for the hydrolysis of
N- (benzyloxycarbonyl) -D (L) -phenylalanyl-L-phenylalanine
p-nitrophenyl ester (Z-D (L) -Phe-L-Phe-PNP) by γ-CyD. Furthermore, the computer modeling (MOPAC calculation) study suggests that a favorable molecular recognition between the substrate and catalyst through the effective hydrophobic interactions and hydrogen bonds should be very important for the enhancement of stereoselectivity.
抄録全体を表示