L-Threonine Transaldolase Activity Is Enabled by a Persistent Catalytic Intermediate.

ABSTRACT: l-Threonine transaldolases (lTTAs) are a poorly characterized class of pyridoxal-5'-phosphate (PLP) dependent enzymes responsible for the biosynthesis of diverse β-hydroxy amino acids. Here, we study the catalytic mechanism of ObiH, an lTTA essential for biosynthesis of the β-lactone natural product obafluorin. Heterologously expressed ObiH purifies as a mixture of chemical states including a catalytically inactive form of the PLP cofactor. Photoexcitation of ObiH promotes the conversion of the inactive state of the enzyme to the active form. UV-vis spectroscopic analysis reveals that ObiH catalyzes the retro-aldol cleavage of l-threonine to form a remarkably persistent glycyl quinonoid intermediate, with a half-life of ∼3 h. Protonation of this intermediate is kinetically disfavored, enab

SUBMITTER: Kumar P 

PROVIDER: S-EPMC8331687 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature