Suppression of water as a nucleophile in Candida antarctica lipase B catalysis.
A water tunnel in Candida antarctica lipase B that provides the active site with substrate water is hypothesized. A small, focused library created in order to prevent water from entering the active site through the tunnel was screened for increased transacylation over hydrolysis activity. A single mutant, S47L, in which the inner part of the tunnel was blocked, catalysed the transacylation of vinyl butyrate to 20 mM butanol 14 times faster than hydrolysis. The single mutant Q46A, which has a more open outer end of the tunnel, showed an increased hydrolysis rate and a decreased hydrolysis to transacylation ratio compared to the wild-type lipase. Mutants with a blocked tunnel could be very useful in applications in which hydrolysis is unwanted, such as the acylation of highly hydrophilic compounds in the presence of water.
Larsen
Marianne Wittrup
MW
Department of Biochemistry, School of Biotechnology, Royal Institute of Technology, AlbaNova University Center, 10691 Stockholm, Sweden.
Zielinska
Dorota F
DF
Martinelle
Mats
M
Hidalgo
Aurelio
A
Jensen
Lars Juhl
LJ
Bornscheuer
Uwe T
UT
Hult
Karl
K
D019943:Amino Acid Substitution; D001665:Binding Sites; D055162:Biocatalysis; D002175:Candida / Q000201:enzymology*; D020134:Catalytic Domain; D003198:Computer Simulation; D005656:Fungal Proteins; D006868:Hydrolysis; D008049:Lipase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014867:Water / Q000737:chemistry*
D005656:Fungal Proteins; D011994:Recombinant Proteins; D014867:Water; D008049:Lipase; C431349:lipase B, Candida antarctica