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Stepwise enhancement of catalytic performance of haloalkane dehalogenase LinB towards β-hexachlorocyclohexane.

Moriuchi R, Tanaka H, Nikawadori Y, Ishitsuka M, Ito M, Ohtsubo Y, Tsuda M, Damborsky J, Prokop Z, Nagata Y - AMB Express (2014)

Bottom Line: Two haloalkane dehalogenases, LinBUT and LinBMI, each with 296 amino acid residues, exhibit only seven amino acid residue differences between them, but LinBMI's catalytic performance towards β-hexachlorocyclohexane (β-HCH) is considerably higher than LinBUT's.To elucidate the molecular basis governing this difference, intermediate mutants between LinBUT and LinBMI were constructed and kinetically characterized.The activities of LinBUT-based mutants gradually increased by cumulative mutations into LinBUT, and the effects of the individual amino acid substitutions depended on combination with other mutations.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Environmental Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan ; The United Graduate School of Agricultural Science, Gifu University 1-1 Yanagido, Gifu 501-1193, Japan.

ABSTRACT
Two haloalkane dehalogenases, LinBUT and LinBMI, each with 296 amino acid residues, exhibit only seven amino acid residue differences between them, but LinBMI's catalytic performance towards β-hexachlorocyclohexane (β-HCH) is considerably higher than LinBUT's. To elucidate the molecular basis governing this difference, intermediate mutants between LinBUT and LinBMI were constructed and kinetically characterized. The activities of LinBUT-based mutants gradually increased by cumulative mutations into LinBUT, and the effects of the individual amino acid substitutions depended on combination with other mutations. These results indicated that LinBUT's β-HCH degradation activity can be enhanced in a stepwise manner by the accumulation of point mutations.

No MeSH data available.


Related in: MedlinePlus

β-HCH degradation reactions catalyzed by LinBUTand LinBMI. LinBMI converts β-HCH to PCHL and further to TCDL, while LinBUT catalyzes only the first conversion step of β-HCH to PCHL.
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Figure 1: β-HCH degradation reactions catalyzed by LinBUTand LinBMI. LinBMI converts β-HCH to PCHL and further to TCDL, while LinBUT catalyzes only the first conversion step of β-HCH to PCHL.

Mentions: An industrial chemical process of benzene photochlorination generates so-called technical-HCH (t-HCH), which consists mainly of five isomers, α- (60-70%), γ- (12-16%), β- (10-12%), δ- (6-10%), and ε-HCH (3-4%) (Vijgen et al. [2011]). Among these isomers, only γ-HCH has insecticidal activity; this isomer was therefore purified. The remaining isomers were in many cases improperly deposited, causing serious environmental problems. α- and β-HCH isomers as well as γ-HCH were categorized as persistent organic pollutants (POPs) at the Stockholm Convention (Vijgen et al. [2011]). Among the HCH isomers, β-HCH is the most recalcitrant; it is usually the predominant isomer remaining in contaminated soils and in animal tissues and fluids (Willett, et al. [1998]). All six chlorines of β-HCH in equatorial positions seem to contribute to its having the greatest chemical stability among the isomers. Several β-HCH-degrading bacterial strains have also been identified (Johri et al. [1998]; Gupta et al. [2000], [2001]). Haloalkane dehalogenase (HLD) LinB, which was originally described as an enzyme involved in γ-HCH degradation in Sphingobium japonicum UT26 (LinBUT) (Nagata et al. [1993]), was more recently identified as an enzyme possessing β-HCH degradation activity (Nagata et al. [2005]; Sharma et al. [2006]) (Figure 1).


Stepwise enhancement of catalytic performance of haloalkane dehalogenase LinB towards β-hexachlorocyclohexane.

Moriuchi R, Tanaka H, Nikawadori Y, Ishitsuka M, Ito M, Ohtsubo Y, Tsuda M, Damborsky J, Prokop Z, Nagata Y - AMB Express (2014)

β-HCH degradation reactions catalyzed by LinBUTand LinBMI. LinBMI converts β-HCH to PCHL and further to TCDL, while LinBUT catalyzes only the first conversion step of β-HCH to PCHL.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4230811&req=5

Figure 1: β-HCH degradation reactions catalyzed by LinBUTand LinBMI. LinBMI converts β-HCH to PCHL and further to TCDL, while LinBUT catalyzes only the first conversion step of β-HCH to PCHL.
Mentions: An industrial chemical process of benzene photochlorination generates so-called technical-HCH (t-HCH), which consists mainly of five isomers, α- (60-70%), γ- (12-16%), β- (10-12%), δ- (6-10%), and ε-HCH (3-4%) (Vijgen et al. [2011]). Among these isomers, only γ-HCH has insecticidal activity; this isomer was therefore purified. The remaining isomers were in many cases improperly deposited, causing serious environmental problems. α- and β-HCH isomers as well as γ-HCH were categorized as persistent organic pollutants (POPs) at the Stockholm Convention (Vijgen et al. [2011]). Among the HCH isomers, β-HCH is the most recalcitrant; it is usually the predominant isomer remaining in contaminated soils and in animal tissues and fluids (Willett, et al. [1998]). All six chlorines of β-HCH in equatorial positions seem to contribute to its having the greatest chemical stability among the isomers. Several β-HCH-degrading bacterial strains have also been identified (Johri et al. [1998]; Gupta et al. [2000], [2001]). Haloalkane dehalogenase (HLD) LinB, which was originally described as an enzyme involved in γ-HCH degradation in Sphingobium japonicum UT26 (LinBUT) (Nagata et al. [1993]), was more recently identified as an enzyme possessing β-HCH degradation activity (Nagata et al. [2005]; Sharma et al. [2006]) (Figure 1).

Bottom Line: Two haloalkane dehalogenases, LinBUT and LinBMI, each with 296 amino acid residues, exhibit only seven amino acid residue differences between them, but LinBMI's catalytic performance towards β-hexachlorocyclohexane (β-HCH) is considerably higher than LinBUT's.To elucidate the molecular basis governing this difference, intermediate mutants between LinBUT and LinBMI were constructed and kinetically characterized.The activities of LinBUT-based mutants gradually increased by cumulative mutations into LinBUT, and the effects of the individual amino acid substitutions depended on combination with other mutations.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Environmental Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan ; The United Graduate School of Agricultural Science, Gifu University 1-1 Yanagido, Gifu 501-1193, Japan.

ABSTRACT
Two haloalkane dehalogenases, LinBUT and LinBMI, each with 296 amino acid residues, exhibit only seven amino acid residue differences between them, but LinBMI's catalytic performance towards β-hexachlorocyclohexane (β-HCH) is considerably higher than LinBUT's. To elucidate the molecular basis governing this difference, intermediate mutants between LinBUT and LinBMI were constructed and kinetically characterized. The activities of LinBUT-based mutants gradually increased by cumulative mutations into LinBUT, and the effects of the individual amino acid substitutions depended on combination with other mutations. These results indicated that LinBUT's β-HCH degradation activity can be enhanced in a stepwise manner by the accumulation of point mutations.

No MeSH data available.


Related in: MedlinePlus