10.1021/acsomega.7b01435.s001
Ayesha Kashif
Ayesha
Kashif
Lan-Huong Tran
Lan-Huong
Tran
Sei-Heon Jang
Sei-Heon
Jang
ChangWoo Lee
ChangWoo
Lee
Roles of Active-Site Aromatic Residues in Cold Adaptation
of Sphingomonas glacialis Esterase
EstSP1
American Chemical Society
2017
Tyr 191 mutants
stability
enzyme activity
Y 191W
Arctic zone
active-site walls
Cold Adaptation
wild-type EstSP 1.
psychrophilic enzymes
moderate-temperature esterases
extremophilic esterases
temperature adaptation
Tyr 191
phenyl hydroxyl group
Trp residue
Tyr residue
protein structure
Sphingomonas glacialis Esterase EstSP 1
Trp residues
Y 191H mutants
novel insight
PAMC
Active-Site Aromatic Residues
EstSP 1
psychrophilic esterase EstSP 1
2017-12-07 20:18:39
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Roles_of_Active-Site_Aromatic_Residues_in_Cold_Adaptation_of_Sphingomonas_glacialis_Esterase_EstSP1/5682634
The aromatic amino acids, Tyr or
Trp, which line the active-site
walls of esterases, stabilize the catalytic His loop via hydrogen
bonding. A Tyr residue is preferred in extremophilic esterases (psychrophilic
or hyperthermophilic esterases), whereas a Trp residue is preferred
in moderate-temperature esterases. Here, we provide evidence that
Tyr and Trp play distinct roles in cold adaptation of the psychrophilic
esterase EstSP1 isolated from an Arctic bacterium Sphingomonas
glacialis PAMC 26605. Stern–Volmer plots showed
that the mutation of Tyr191 to Ala, Phe, Trp, and His resulted in
reduced conformational flexibility of the overall protein structure.
Interestingly, the Y191W and Y191H mutants showed increased thermal
stability at moderate temperatures. All Tyr191 mutants showed reduced
catalytic activity relative to wild-type EstSP1. Our results indicate
that Tyr with its phenyl hydroxyl group is favored for increased conformational
flexibility and high catalytic activity of EstSP1 at low temperatures
at the expense of thermal stability. The results of this study suggest
that, in the permanently cold Arctic zone, enzyme activity has been
selected for psychrophilic enzymes over thermal stability. The results
presented herein provide novel insight into the roles of Tyr and Trp
residues for temperature adaptation of enzymes that function at low,
moderate, and high temperatures.