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

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