The evolution of catalytic efficiency and substrate promiscuity in human theta class 1-1 glutathione transferase.

ABSTRACT: Theta class glutathione transferases (GST) from various species exhibit markedly different catalytic activities in conjugating the tripeptide glutathione (GSH) to a variety of electrophilic substrates. For example, the human theta 1-1 enzyme (hGSTT1-1) is 440-fold less efficient than the rat theta 2-2 enzyme (rGSTT2-2) with the fluorogenic substrate 7-amino-4-chloromethyl coumarin (CMAC). Large libraries of hGSTT1-1 constructed by error-prone PCR, DNA shuffling, or saturation mutagenesis were screened for improved catalytic activity towards CMAC in a quantitative fashion using flow cytometry. An iterative directed evolution approach employing random mutagenesis in conjunction with homologous recombination gave rise to enzymes exhibiting up to a 20,000-fold increase in k(cat)/K(M) compared

SUBMITTER: Griswold KE 

PROVIDER: S-EPMC1995603 | biostudies-literature | 2006 Dec

REPOSITORIES: biostudies-literature