Exploring donor substrate promiscuity of a Thermostable Transketolase by directed evolution
September 24-28, 2017
Enzymes catalyzing asymmetric carboligation reactions typically show very high specificity for their nucleophilic substrate. Transketolase (TK, EC 22.214.171.124) catalyses a reversible transfer of a hydroxylated C2 fragment among phosphorylated ketoses and aldoses.  Native TK converts a large variety of (2R)-hydroxyaldehydes as the electrophilic acceptor substrates, but apart from its natural phosphoketose donors TK accepts only hydroxypyruvate (hydroxylated donor) (Figure 1). In contrast, 1-deoxy-D-xylulose-5-phosphate synthase (DXS, EC 126.96.36.199) catalyzes the specific decarboxylative transfer of the acetyl moiety from pyruvate (non-hydroxylated donor) to glyceraldehyde-3-phosphate to yield 1-deoxy-D-xylulose 5-phosphate (DXP), which constitutes the first step into the non-mevalonate biosynthesis of terpenoids (Figure 1). Reactions of native TK and DXS are mutually exclusive in vivo.
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Thangavelu Saravanan and Wolf-Dieter Fessner, "Exploring donor substrate promiscuity of a Thermostable Transketolase by directed evolution" in "Enzyme Engineering XXIV", Pierre Monsan, Toulouse White Biotechnology, France Magali Remaud-Simeon, LISBP-INSA, University of Toulouse, France Eds, ECI Symposium Series, (2017). http://dc.engconfintl.org/enzyme_xxiv/2