Threonine Aldolases

Franz, Sarah E.; Stewart, Jon D.

doi:10.1016/b978-0-12-800260-5.00003-6

Cited by 44 publications

(47 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The utility of L -TAs for the enzymatic synthesis of L - threo -β-hydroxy-α-amino acids from an aldehyde and glycine has been extensively investigated, but is limited due to low synthetic yields and modest diastereoselectivity1011. The low yields are in part due to the reversible nature of the reaction (retroaldol cleavage of L - threo -β-hydroxy-α-amino acids) and an equilibrium which favours aldehyde and glycine.…”

Section: Discussionmentioning

confidence: 99%

“…Although many different synthetic methods have been reported for their chemical synthesis—including methods based on glycine enolates6, glycinamides7, glycine Schiff’s base8 and the aminohydroxylation of olefins9—the production of β-hydroxy-α-amino acids by enzymatic means is particularly attractive as these can set two stereocentres in a single reaction that can be performed in a one-pot process with minimal protection of substrates and under mild, aqueous conditions. One such example is found in the threonine aldolases (TAs) although their utility is limited due to low synthetic yields and modest diastereoselectivity (they are highly stereoselective for the α-carbon)101112. As such the discovery and characterization of new enzymes with utility for the synthesis of β-hydroxy-α-amino acids is desirable to expand our toolkit for asymmetric synthesis.…”

mentioning

confidence: 99%

See 1 more Smart Citation

An L-threonine transaldolase is required for L-threo-β-hydroxy-α-amino acid assembly during obafluorin biosynthesis

et al. 2017

View full text Add to dashboard Cite

β-Lactone natural products occur infrequently in nature but possess a variety of potent and valuable biological activities. They are commonly derived from β-hydroxy-α-amino acids, which are themselves valuable chiral building blocks for chemical synthesis and precursors to numerous important medicines. However, despite a number of excellent synthetic methods for their asymmetric synthesis, few effective enzymatic tools exist for their preparation. Here we report cloning of the biosynthetic gene cluster for the β-lactone antibiotic obafluorin and delineate its biosynthetic pathway. We identify a nonribosomal peptide synthetase with an unusual domain architecture and an L-threonine:4-nitrophenylacetaldehyde transaldolase responsible for (2S,3R)-2-amino-3-hydroxy-4-(4-nitrophenyl)butanoate biosynthesis. Phylogenetic analysis sheds light on the evolutionary origin of this rare enzyme family and identifies further gene clusters encoding L-threonine transaldolases. We also present preliminary data suggesting that L-threonine transaldolases might be useful for the preparation of L-threo-β-hydroxy-α-amino acids.

show abstract

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

An L-threonine transaldolase is required for L-threo-β-hydroxy-α-amino acid assembly during obafluorin biosynthesis

et al. 2017

View full text Add to dashboard Cite

show abstract

“…g . acetaldehyde) [ 1 ]. Threonine aldolases show a high selectivity for the absolute configuration at the Cα atom, but generally possess only moderate stereoselectivity at the β-carbon ( Fig 1 ).…”

Section: Introductionmentioning

confidence: 99%

The Crystal Structure of D-Threonine Aldolase from Alcaligenes xylosoxidans Provides Insight into a Metal Ion Assisted PLP-Dependent Mechanism

et al. 2015

View full text Add to dashboard Cite

Threonine aldolases catalyze the pyridoxal phosphate (PLP) dependent cleavage of threonine into glycine and acetaldehyde and play a major role in the degradation of this amino acid. In nature, L- as well as D-specific enzymes have been identified, but the exact physiological function of D-threonine aldolases (DTAs) is still largely unknown. Both types of enantio-complementary enzymes have a considerable potential in biocatalysis for the stereospecific synthesis of various β-hydroxy amino acids, which are valuable building blocks for the production of pharmaceuticals. While several structures of L-threonine aldolases (LTAs) have already been determined, no structure of a DTA is available to date. Here, we report on the determination of the crystal structure of the DTA from Alcaligenes xylosoxidans (AxDTA) at 1.5 Å resolution. Our results underline the close relationship of DTAs and alanine racemases and allow the identification of a metal binding site close to the PLP-cofactor in the active site of the enzyme which is consistent with the previous observation that divalent cations are essential for DTA activity. Modeling of AxDTA substrate complexes provides a rationale for this metal dependence and indicates that binding of the β-hydroxy group of the substrate to the metal ion very likely activates this group and facilitates its deprotonation by His193. An equivalent involvement of a metal ion has been implicated in the mechanism of a serine dehydratase, which harbors a metal ion binding site in the vicinity of the PLP cofactor at the same position as in DTA. The structure of AxDTA is completely different to available structures of LTAs. The enantio-complementarity of DTAs and LTAs can be explained by an approximate mirror symmetry of crucial active site residues relative to the PLP-cofactor.

show abstract

“…They have the ability to catalyze the formation of the α-carbon center with excellent stereoselectivity by formation of two stereogenic centers in one step starting from two prochiral precursors, but lacking high stereochemical control at the β-carbon (Clapés and Garrabou 2011;Dückers et al 2010;Franz and Stewart 2014). New TAs can be obtained, for example, by screening among wild-type strains or metagenomic or mutant libraries.…”

Section: Discussionmentioning

confidence: 98%

Development of a growth-dependent selection system for identification of l-threonine aldolases

Bulut

Gröger

Hummel

2015

Appl Microbiol Biotechnol

View full text Add to dashboard Cite

Threonine aldolases (TAs) are useful enzymes for the synthesis of β-hydroxy-α-amino acids due to their capability to catalyze asymmetric aldol reactions. Starting from two prochiral compounds, an aldehyde and glycine, two chiral stereocenters were formed in a single step via C-C bond formation. Owing to poor diastereoselectivity and low activity, the enzymatic synthesis of β-hydroxy-α-amino acids by TAs is still a challenge. For identification of new TAs, a growth-dependent selection system in Pseudomonas putida KT2440 has been developed. This bacterium is able to use aromatic compounds such as benzaldehyde, which is the cleavage product of the TA-mediated retro-aldol reaction of phenylserine, as sole carbon source via the β-ketoadipate pathway. With DL-threo-β-phenylserine as sole carbon source, this strain showed only slight growth in minimal medium. This growth deficiency can be restored by introducing and expressing genes encoding TAs. In order to develop a highly efficient selection system, the gene taPp of P. putida KT2440 encoding a TA was successfully deleted by replacement with an antibiotic resistance cassette. Different growth studies were carried out to prove the operability of the selection system. Genes encoding for L- and D-specific TAs (L-TA genes of Escherichia coli (ltaE) and Saccharomyces cerevisiae (gly1) and D-TA gene of Achromobacter xylosoxidans (dtaAX)) were introduced into the selection strain P. putida KT2440ΔtaPp, followed by cultivation on minimal medium supplemented with DL-threo-β-phenylserine. The results demonstrate that only the selection strains with plasmid-encoded L-TAs were able to grow on this racemic amino acid, whereas the corresponding strain harboring the gene coding for a D-specific TA showed no growth. In summary, it can be stated that a powerful screening tool was developed to identify easily by growth new L-specific threonine aldolases or other enzymes from genomic or metagenomic libraries liberating benzaldehyde.

show abstract

Threonine Aldolases

Cited by 44 publications

References 33 publications

An L-threonine transaldolase is required for L-threo-β-hydroxy-α-amino acid assembly during obafluorin biosynthesis

An L-threonine transaldolase is required for L-threo-β-hydroxy-α-amino acid assembly during obafluorin biosynthesis

The Crystal Structure of D-Threonine Aldolase from Alcaligenes xylosoxidans Provides Insight into a Metal Ion Assisted PLP-Dependent Mechanism

Development of a growth-dependent selection system for identification of l-threonine aldolases

Contact Info

Product

Resources

About