Stereochemical course of dehydration catalysed by the yeast fatty acid synthetase

Sedgwick, Brian; Morris, Caroline; French, Sidney J.

doi:10.1039/c39780000193

Cited by 41 publications

(38 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is in contrast to the demonstrated specificity of EryDH4, TylDH2, and NanDH2, all of which utilize only (2 R ,3 R )-2-methyl-3-hydroxyacyl-ACP substrates, as well as the specificity of the DH domain of yeast FAS for 3 R -hydroxyacyl-ACP substrates. 55 Intriguingly, the intrinsic preference of RifDH10 for the (2 S ,3 S )-2-methyl-3-hydroxyacyl thioesters is only evident when the substrate is tethered to its native acyl carrier protein, RifACP10. By contrast, RifDH10-catalyzed dehydration of the corresponding non-cognate EryACP6, as well as the NAC and pantetheine thioester analogues is specific for the corresponding (2 R ,3 R )-2-methyl-3-hydroxyacyl diastereomers, while in no case do either the (2 R ,3 S )- or (2 S ,3 R )-2-methyl-3-hydroxyacyl derivatives undergo dehydration.…”

Section: Discussionmentioning

confidence: 99%

Structure and Stereospecificity of the Dehydratase Domain from the Terminal Module of the Rifamycin Polyketide Synthase

et al. 2013

View full text Add to dashboard Cite

RifDH10, the dehydratase domain from the terminal module of the rifamycin polyketide synthase, catalyzed the stereospecific syn dehydration of the model substrate (2S,3S)-2-methyl-3-hydroxypentanoyl-RifACP10, resulting in exclusive formation of (E)-2-methyl-2-pentenoyl-RifACP10. RifDH10 did not dehydrate any of the other three diastereomeric, RifACP10-bound, diketide thioester substrates. On the other hand, when EryACP6, from the sixth module of the erythromycin polyketide synthase, was substituted for RifACP10, RifDH10 stereospecifically dehydrated only (2R,3R)-2-methyl-3-hydroxypentanoyl-EryACP6 to give exclusively (E)-2-methyl-2-pentenoyl-EryACP6, with no detectable dehydration of any of the other three diastereomeric, EryACP6-bound, diketides. An identical alteration in substrate diastereospecificity was observed for the corresponding N-acetylcysteamine or pantetheine thioester analogues, regardless of acyl chain length or substitution pattern. Incubation of (2RS)-2-methyl-3-ketopentanoyl-RifACP10 with the didomain reductase-dehydratase RifKR10-RifDH10 yielded (E)-2-methyl-2-pentenoyl-RifACP10, the expected product of syn dehydration of (2S,3S)-2-methyl-3-hydroxypentanoyl-RifACP10, while incubation with the corresponding EryACP6-bound substrate, (2RS)-2-methyl-3-ketopentanoyl-EryACP6, gave only the reduction product (2S,3S)-2-methyl-3-hydroxypentanoyl-EryACP6 with no detectable dehydration. These results establish the intrinsic syn dehydration stereochemistry and substrate diastereoselectivity of RifDH10 and highlight the critical role of the natural RifACP10 domain in chaperoning the proper recognition and processing of the natural ACP-bound undecaketide substrate. The 1.82 Å-resolution structure of RifDH10 revealed the atomic resolution details of the active site and allowed modeling of the syn-dehydration of the (2S,3S)-2-methyl-3-hydroxyacyl-RifACP10 substrate. These results suggest that generation of the characteristic cis double bond of the rifamycins occurs after formation of the full-length RifACP10-bound acyclic trans-unsaturated undecaketide intermediate, most likely during the subsequent macrolactamization catalyzed by the amide synthase RifF.

show abstract

Section: Discussionmentioning

confidence: 99%

Structure and Stereospecificity of the Dehydratase Domain from the Terminal Module of the Rifamycin Polyketide Synthase

et al. 2013

View full text Add to dashboard Cite

show abstract

“…18 The structure of the E. coli dehydratase (FabA) displays a characteristic hotdog fold that has been observed in all other DH structures from both FAS and PKS systems. 7a,19,20 The active site of each DH harbors a universally conserved pair of His and Asp residues.…”

Section: Discussionmentioning

confidence: 96%

“…Schwab, in a critical review of research on FabA and the closely related dehydratase-isomerase FabZ, has discussed a one-base, two-step mechanistic model in which the active site imidazole residue first catalyzes the stereospecific removal of 2-H si of the 3-hydroxyacyl-ACP substrate following which the transiently-generated imidazolium species donates its proton to the 3-hydroxyl group to promote C–O bond cleavage. 18a,21,22 Although the distinct enoyl-CoA hydratase of fatty acid oxidation differs significantly from DH enzymes in both protein fold and the presence of two essential active site Glu residues in place of the His-Asp dyad of DH domains, it catalyzes an analogous net syn hydration of ( E )-2-enoyl-CoA thioesters to yield the corresponding (3 S )-3-hydroxyacyl-CoA products. 17a Both protons and the oxygen of the nucleophilic water are incorporated into the product, consistent with a single-base mechanism for enoyl-CoA hydratase in which one Glu residue acts sequentially, first as base and then as active site acid, while the second Glu side chain positions the active site water by an essential H-bond.…”

Section: Discussionmentioning

confidence: 99%

Stereospecific Formation of E- and Z-Disubstituted Double Bonds by Dehydratase Domains from Modules 1 and 2 of the Fostriecin Polyketide Synthase

2017

View full text Add to dashboard Cite

The dehydratase domain FosDH1 from module 1 of the fostriecin polyketide synthase (PKS) catalyzed the stereospecific interconversion of (3R)-3-hydroxybutyryl-FosACP1 (5) and (E)-2-butenoyl-FosACP1 (11), as established by a combination of direct LC-MS/MS and chiral GC-MS. FosDH1 did not act on either (3S)-3-hydroxybutyryl-FosACP1 (6) or (Z)-2-butenoyl-FosACP1 (12). FosKR2, the ketoreductase from module 2 of the fostriecin PKS that normally provides the natural substrate for FosDH2, was shown to catalyze the NADPH-dependent stereospecific reduction of 3-ketobutyryl-FosACP2 (23) to (3S)-3-hydroxybutyryl-FosACP2 (8). Consistent with this finding, FosDH2 catalyzed the interconversion of the corresponding triketide substrates (3R,4E)-3-hydroxy-4-hexenoyl-FosACP2 (18) and (2Z,4E)-2,4-hexadienoyl-FosACP2 (21). FosDH2 also catalyzed the stereospecific hydration of (Z)-2-butenoyl-FosACP2 (14) to (3S)-3-hydroxybutyryl-FosACP2 (8). Although incubation of FosDH2 with (3S)-3-hydroxybutyryl-FosACP2 (8) did not result in detectable accumulation of (Z)-2-butenoyl-FosACP2 (14), FosDH2 catalyzed the slow exchange of the 3-hydroxy group of 8 with [18O]-water. FosDH2 unexpectedly could also support the stereospecific interconversion of (3R)-3-hydroxybutyryl-FosACP2 (7) and (E)-2-butenoyl-FosACP2 (13).

show abstract

“…Aside from this study, no other reports probe the substrate preference or catalytic mechanism of DH domains within PKS systems; therefore, much of what is known has been elucidated from studies of fatty acid biosynthesis (28). Previous studies on the dehydration step that is catalyzed by the yeast fatty acid synthase confirmed the syn elimination of water from a D-(3 R)-hydroxyacylthioester substrate (29). This result is consistent with the stereospecificity of the PKS DH domain and may suggest that trans unsaturated bonds, typically found in polyketides, are likewise formed via syn water elimination.…”

Section: Trans Double Bondsmentioning

confidence: 97%

Modular Polyketide Synthases

Buchholz

Kittendorf

Sherman

2012

Natural Products in Chemical Biology

View full text Add to dashboard Cite

Stereochemical course of dehydration catalysed by the yeast fatty acid synthetase

Abstract: Dehydration of the (3R)-hydroxyalkyl S-thioester (1) by yeast fatty acid synthetase to give the trans-2-enoyl derivative (2) occurs by means of a synelimination of the elements of water.

Cited by 41 publications

References 0 publications

Structure and Stereospecificity of the Dehydratase Domain from the Terminal Module of the Rifamycin Polyketide Synthase

Structure and Stereospecificity of the Dehydratase Domain from the Terminal Module of the Rifamycin Polyketide Synthase

Stereospecific Formation of E- and Z-Disubstituted Double Bonds by Dehydratase Domains from Modules 1 and 2 of the Fostriecin Polyketide Synthase

Modular Polyketide Synthases

Contact Info

Product

Resources

About