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- Holmquist, Mats Torsten, et al.
(författare)
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Lipases from Rhizomucor miehei and Humicola lanuginosa : Modification of the lid covering the active site alters enantioselectivity
- 1993
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Ingår i: Journal of Protein Chemistry. - 0277-8033. ; 12:6, s. 749-757
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Tidskriftsartikel (refereegranskat)abstract
- The homologous lipases from Rhizomucor miehei and Humicola lanuginosa showed approximately the same enantioselectivity when 2-methyldecanoic acid esters were used as substrates. Both lipases preferentially hydrolyzed the S- enantiomer of 1-heptyl 2-methyldecanoate (R. miehei: E(S) = 8.5; H. lanuginosa: E(S) = 10.5), but the R-enantiomer of phenyl 2-methyldecanoate (E(R) = 2.9). Chemical arginine specific modification of the R. miehei lipase with 1,2-cyclohexanedione resulted in a decreased enantioselectivity (E(R) = 2.0), only when the phenyl ester was used as a substrate. In contrast, treatment with phenylglyoxal showed a decreased enantioselectivity (E(S) = 2.5) only when the heptyl ester was used as a substrate. The presence of guanidine, an arginine side chain analog, decreased the enantioselectivity with the heptyl ester (E(S) = 1.9) and increased the enantioselectivity with the aromatic ester (E(R) = 4.4) as substrates. The mutation, Glu 87 Ala, in the lid of the H. lanuginosa lipase, which might decrease the electrostatic stabilization of the open-lid conformation of the lipase, resulted in 47% activity compared to the native lipase, in a tributyrin assay. The Glu 87 Ala mutant showed an increased enantioselectivity with the heptyl ester (E(S) = 17.4) and a decreased enantioselectivity with the phenyl ester (E(R) = 2.5) as substrates, compared to native lipase. The enantioselectivities of both lipases in the esterification of 2-methyldecanoic acid with 1-heptanol were unaffected by the lid modifications.
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| 2. |
- Berglund, Per, et al.
(författare)
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2-Methylalkanoic acids resolved by esterification catalysed by lipase from Candida rugosa : Alcohol chain length and enantioselectivity
- 1993
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Ingår i: Tetrahedron Asymmetry. - 0957-4166. ; 4:8, s. 1869-1878
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Tidskriftsartikel (refereegranskat)abstract
- Enantiomerically pure (R)-2-methyldecanoic acid and (S)-2-methyl-1-decanol were prepared in a multi gram scale by esterification reactions catalysed by lipase from Candida rugosa. The enantiomeric ratios (E-values) were determined as a function of the chain length of the alcohol used as the complementary substrate in cyclohexane. In the resolution of 2-methyldecanoic acid the highest value (E = 37 ± 5) was obtained, when either 2-hexanol, 1-heptanol or 1-octanol were used. In contrast, when resolving 2-methyloctanoic acid, the E-values increased continually with increasing chain length of the alcohol used. 1-Hexadecanol gave the highest value: E > 100. The E-values were determined from the enantiomeric excess (ee) of the product at a conversion below 0.4. After two consecutive esterification reactions enantiomerically pure (R)-2-methyldecanoic acid, >99.8% ee, and after subsequent reduction of the ester produced, (S)-2-methyl-1-decanol, 96.7% ee, were obtained.
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