Lipases from Rhizomucor miehei and Humicola lanuginosa: modification of the lid covering the active site alters enantioselectivity.
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: ES = 8.5; H. lanuginosa: ES = 10.5), but the R-enantiomer of phenyl 2-methyldecanoate (ER = 2.9). Chemical arginine specific modification of the R. miehei lipase with 1,2-cyclohexanedione resulted in a decreased enantioselectivity (ER = 2.0), only when the phenyl ester was used as a substrate. In contrast, treatment with phenylglyoxal showed a decreased enantioselectivity (ES = 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 (ES = 1.9) and increased the enantioselectivity with the aromatic ester (ER = 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 (ES = 17.4) and a decreased enantioselectivity with the phenyl ester (ER = 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.
Holmquist
M
M
Department of Biochemistry and Biotechnology, Royal Institute of Technology, Stockholm, Sweden.
Martinelle
M
M
Berglund
P
P
Clausen
I G
IG
Patkar
S
S
Svendsen
A
A
Hult
K
K
D001120:Arginine; D003512:Cyclohexanones / Q000494:pharmacology; D003651:Decanoates / Q000378:metabolism; D004800:Enzymes, Immobilized / Q000378:metabolism*; D006868:Hydrolysis; D007700:Kinetics; D008049:Lipase / Q000378:metabolism*; D003904:Mitosporic Fungi / Q000201:enzymology*; D009090:Mucorales / Q000201:enzymology*; D010658:Phenylglyoxal / Q000494:pharmacology; D013237:Stereoisomerism; D013379:Substrate Specificity
D003512:Cyclohexanones; D003651:Decanoates; D004800:Enzymes, Immobilized; C018031:1,2-cyclohexanedione; D001120:Arginine; D008049:Lipase; D010658:Phenylglyoxal