Use of aromatic thia fatty acids as active site mapping agents for a yeast Δ9 desaturase

1994 ◽  
Vol 72 (1) ◽  
pp. 176-181 ◽  
Author(s):  
Peter H. Buist ◽  
Dale M. Marecak
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Fatty Acids ◽  
Active Site ◽  
Optical Purity ◽  
Shift Reagent ◽  
Chiral Shift Reagent ◽  
Site Mapping ◽  
Δ9 Desaturase ◽  
Conformational Model ◽  
Thia Fatty Acids

The Δ9 desaturating system of Saccharomyces cerevisiae can sulfoxidize methyl S-benzyl-8-mercaptooctanoate as well as its naphthyl analogue but the corresponding isomers where sulfur is bonded to the aromatic ring do not function as substrates. We have accounted for these results in terms of a conformational model. We have also accumulated some evidence that suggests that dealkylation of these thia analogues does not compete with sulfoxidation. Our recently discovered chiral shift reagent (S)-(+)-α-methoxyphenylacetic acid (MPAA) can be used to determine the optical purity and absolute configuration of all sulfoxides prepared in this work.

Optical Purity Determination and 1H NMR Spectral Simplification with Lanthanide Shift Reagents: Glutethimide, 3-Ethyl-3-phenyl-2,6-piperidinedione, 1

1983 ◽  
Vol 37 (3) ◽  
pp. 292-296 ◽  
Author(s):  
Suzanne Eberhart ◽  
Robert Rothchild
Keyword(s):  
Aromatic Ring ◽  
Optical Purity ◽  
Shift Reagent ◽  
Coupling Constants ◽  
Line Broadening ◽  
Molar Ratios ◽  
H Nmr ◽  
A Value ◽  
Chiral Shift Reagent ◽  
Lanthanide Shift Reagents

The 60 MHz 1H NMR spectra of racemic glutethimide, 1, have been studied with the chiral shift reagent, tris[3-(trifluoromethylhydroxymethylene)- d-camphorato] europium(III), 2, and the achiral tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato) europium(III), 3. Appreciable values of the enantiomeric shift difference, ΔΔδ, were observed at relatively low molar ratios of 2:1 for the CH3 group in CDCl3 solution at 28°C. Optical purity determinations should easily be carried out by using this absorption with a 2:1 ratio of approximately 0.25; 3 to 5% of one enantiomer should be detectable in a sample. Lanthanide-induced line broadening was relatively low, thereby facilitating these measurements. A substantial ΔΔδ was also observed for the ortho hydrogens of the aromatic ring and the NH. For example, at a 2:1 ratio of 0.254, the CH3 resonance displayed a value of ΔΔδ of 7.3 Hz (0.12 δ) and was free of overlap with the absorptions of the shift reagent, 2. The relative slopes of the plots of induced shift, Δδ, vs molar ratios of 2:1 or 3:1, as well as values of coupling constants, support assignments for the proton absorptions of the aromatic ring.

Lanthanide Induced Enhancement of Enantiomeric Shifts in Chiral Solvents and its Use in the Determination of Optical Purity

1973 ◽  
Vol 51 (22) ◽  
pp. 3726-3732 ◽  
Author(s):  
C. P. R. Jennison ◽  
Donald Mackay
Keyword(s):  
Chemical Shift ◽  
Fractional Crystallization ◽  
Sulfonic Acid ◽  
Optical Purity ◽  
Shift Reagent ◽  
Lanthanide Shift Reagent ◽  
Chemical Shift Difference ◽  
Chiral Shift Reagent ◽  
Simple Molecules

The chemical shift difference (Δv) between corresponding groups in enantiomers in the presence of both a chiral solvent ((−)-2,2,2-trifluorophenylethanol or (+)-1-phenylethylamine) and an achiral lanthanide shift reagent (Eu(dpm)3 or Eu(fod)3) is much greater than in the chiral solvent alone. In general, for simple molecules having one coordination site the Δv was smaller than that obtained with the chiral shift reagent Eu(HFC)3. Comparable values of Δv, however, were obtained with the 1,3,4-oxadiazine derivatives 4a and b, and 5, suggesting that the "chiral solvate shift system" is best suited to differentiating more complex enantiomers having several coordination sites.The shift system was used to determine the optical purity of two partially resolved substances. One of these was the (+)-oxadiazine 4a, produced in the asymmetric isomerization of the bridged pyridazine 3a by (+)-camphor-10-sulfonic acid, and optically enriched by only one fractional crystallization. The enantiomeric enrichment in the isomerization was 4.21 ± 0.08%.

scholarly journals A non-canonical Δ9-desaturase synthesizing palmitoleic acid identified in the thraustochytrid Aurantiochytrium sp. T66

2021 ◽  
Author(s):  
E-Ming Rau ◽  
Inga Marie Aasen ◽  
Helga Ertesvåg
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Fatty Acid Synthase ◽  
Palmitoleic Acid ◽  
Unsaturated Fatty Acids ◽  
Gene Annotation ◽  
Vaccenic Acid ◽  
Strain Engineering ◽  
Δ9 Desaturase ◽  
Δ12 Desaturase

Abstract Thraustochytrids are oleaginous marine eukaryotic microbes currently used to produce the essential omega-3 fatty acid docosahexaenoic acid (DHA, C22:6 n-3). To improve the production of this essential fatty acid by strain engineering, it is important to deeply understand how thraustochytrids synthesize fatty acids. While DHA is synthesized by a dedicated enzyme complex, other fatty acids are probably synthesized by the fatty acid synthase, followed by desaturases and elongases. Which unsaturated fatty acids are produced differs between different thraustochytrid genera and species; for example, Aurantiochytrium sp. T66, but not Aurantiochytrium limacinum SR21, synthesizes palmitoleic acid (C16:1 n-7) and vaccenic acid (C18:1 n-7). How strain T66 can produce these fatty acids has not been known, because BLAST analyses suggest that strain T66 does not encode any Δ9-desaturase-like enzyme. However, it does encode one Δ12-desaturase-like enzyme. In this study, the latter enzyme was expressed in A. limacinum SR21, and both C16:1 n-7 and C18:1 n-7 could be detected in the transgenic cells. Our results show that this desaturase, annotated T66Des9, is a Δ9-desaturase accepting C16:0 as a substrate. Phylogenetic studies indicate that the corresponding gene probably has evolved from a Δ12-desaturase-encoding gene. This possibility has not been reported earlier and is important to consider when one tries to deduce the potential a given organism has for producing unsaturated fatty acids based on its genome sequence alone. Key points • In thraustochytrids, automatic gene annotation does not always explain the fatty acids produced. • T66Des9 is shown to synthesize palmitoleic acid (C16:1 n-7). • T66des9 has probably evolved from Δ12-desaturase-encoding genes.

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