Isotopic Labelling Experiments and Enzymatic Preparation of Iso-Casbenes with Casbene Synthase from Ricinus communis

2022 ◽  
Author(s):  
Heng Li ◽  
Jeroen Dickschat
Keyword(s):  
Ricinus Communis ◽  
Enzyme Mechanism ◽  
Enzymatic Preparation ◽  
Isotopic Labelling ◽  
Isotopic Labelling Experiments

Isotopic labelling experiments gave insights into the enzyme mechanism of casbene synthase from Ricinus communis, showing a clear stereochemical course for the cyclisation reaction, in agreement with the reported absolute...

Isoishwarane synthase from Streptomyces lincolnensis

2021 ◽  
Author(s):  
Houchao Xu ◽  
Jan Rinkel ◽  
Jeroen S. Dickschat
Keyword(s):  
Natural Product ◽  
Enzyme Mechanism ◽  
Site Directed Mutagenesis ◽  
Terpene Synthase ◽  
Directed Mutagenesis ◽  
Isotopic Labelling ◽  
Streptomyces Lincolnensis ◽  
Isotopic Labelling Experiments

The product of a terpene synthase from Streptomyces lincolnensis has been identified as the new natural product isoishwarane. The enzyme mechanism was studied by isotopic labelling experiments and site-directed mutagenesis.

scholarly journals The enzyme mechanism of patchoulol synthase

2022 ◽  
Vol 18 ◽  
pp. 13-24
Author(s):  
Houchao Xu ◽  
Bernd Goldfuss ◽  
Gregor Schnakenburg ◽  
Jeroen S Dickschat
Keyword(s):  
Computational Chemistry ◽  
Natural Product ◽  
Enzyme Mechanism ◽  
Farnesyl Pyrophosphate ◽  
Isotopic Labelling ◽  
Isotopic Labelling Experiments

Different mechanisms for the cyclisation of farnesyl pyrophosphate to patchoulol by the patchoulol synthase are discussed in the literature. They are based on isotopic labelling experiments, but the results from these experiments are contradictory. The present work reports on a reinvestigation of patchoulol biosynthesis by isotopic labelling experiments and computational chemistry. The results are in favour of a pathway through the neutral intermediates germacrene A and α-bulnesene that are both reactivated by protonation for further cyclisation steps, while previously discussed intra- and intermolecular hydrogen transfers are not supported. Furthermore, the isolation of the new natural product (2S,3S,7S,10R)-guaia-1,11-dien-10-ol from patchouli oil is reported.

Stereochemical Characterisation of the Non-Canonical α-Humulene Synthase from Acremonium strictum

2021 ◽  
Author(s):  
Houchao Xu ◽  
Carsten Schotte ◽  
Russell Cox ◽  
Jeroen Dickschat
Keyword(s):  
Isotopic Labelling ◽  
Acremonium Strictum ◽  
The Face ◽  
Face Selectivity ◽  
Isotopic Labelling Experiments

The non-canonical fungal α-humulene synthase was investigated through isotopic labelling experiments for its stereochemical course regarding inversion or retention at C-1, the face selectivity at C-11, and the stereoselectivity of...

On the mechanism of ophiobolin F synthase and the absolute configuration of its product by isotopic labelling experiments

2020 ◽  
Vol 18 (31) ◽  
pp. 6072-6076 ◽  
Author(s):  
Zhiyang Quan ◽  
Jeroen S. Dickschat
Keyword(s):  
Absolute Configuration ◽  
Isotopic Labelling ◽  
The Absolute ◽  
Isotopic Labelling Experiments

The cyclisation mechanism of ophiobolin F synthase AcldOS and the absolute configuration of its product were investigated by isotopic labelling experiments.

Role of glutamine synthetase in phenazine antibiotic production by Pantoea agglomerans Eh1087

2004 ◽  
Vol 50 (10) ◽  
pp. 877-881 ◽  
Author(s):  
Matthew D Galbraith ◽  
Stephen R Giddens ◽  
H Khris Mahanty ◽  
Bruce Clark
Keyword(s):  
Glutamine Synthetase ◽  
Antibiotic Production ◽  
Amino Acid Sequences ◽  
Pantoea Agglomerans ◽  
Wild Type ◽  
Isotopic Labelling ◽  
High Degree ◽  
Degree Of Similarity ◽  
Isotopic Labelling Experiments

Pantoea agglomerans strain Eh1087 produces the phenazine antibiotic D-alanylgriseoluteic acid. A glutamine auxotroph harboring an insertion in a putative glnA gene was obtained by transposon-mutagenesis of Eh1087 that produced less D-alanylgriseoluteic acid than the parental strain (strain Eh7.1). Cosmids encoding the Eh1087 glnA were isolated by their ability to complement the mutant for prototrophy. The role of the Eh1087 glnA locus was functionally confirmed by complementation of an Escherichia coli glnA mutant. Analysis of the nucleotide and deduced amino acid sequences of the Eh1087 glnA gene indicated a high degree of similarity to the glnA genes and glutamine synthetase enzymes of other Enterobacteriaceae. Isotopic labelling experiments with 15N-labelled ammonium sulfate demonstrated that wild-type Eh1087 incorporated 15N into griseoluteic acid more readily than the glnA mutant Eh7.1. We conclude that the 2 nitrogens in the phenazine nucleus originate from glutamine and the intracellular glutamine synthesized by Eh1087 is a source of the phenazine nucleus nitrogens even in glutamine-rich environments.Key words: phenazine, Pantoea, Erwinia, glutamine synthetase, biosynthesis.

scholarly journals A Boron-Boron Double Transborylation Strategy for the Synthesis of gem-Diborylalkanes

2020 ◽  
Author(s):  
Jamie Docherty ◽  
Kieran Nicholson ◽  
Andrew P Dominey ◽  
Stephen Thomas
Keyword(s):  
Transition State ◽  
Thermodynamic Parameters ◽  
Terminal Alkynes ◽  
Isotopic Labelling ◽  
Wide Range ◽  
Boronic Esters ◽  
Isotopic Labelling Experiments

9-Borabicyclo[3.3.1]nonane (H-<i>B</i>-9-BBN) has been used as a catalyst for the sequential double hydroboration of alkynes with pinacolborane (HBpin) to give alkyl gem-di-pinacol boronic esters. This strategy, which is effective for a wide range of terminal alkynes, is predicated upon a key C(<i>sp</i><sup>3</sup>)-B / B-H transborylation reaction. Transition-state thermodynamic parameters and 10-boron-isotopic labelling experiments are indicative of an <i>σ</i>-bond metathesis exchange pathway.

Novel gas-phase ions. The radical cations [CH2XH]+• (X = F, Cl, Br, I, OH, NH2, SH) and [CH2CH2NH3]+•

1983 ◽  
Vol 61 (10) ◽  
pp. 2305-2309 ◽  
Author(s):  
John L. Holmes ◽  
F. P. Lossing ◽  
Johan K. Terlouw ◽  
Peter C. Burgers
Keyword(s):  
Energy Requirement ◽  
Radical Cations ◽  
Isotopic Labelling ◽  
Ionisation Mass Spectrometry ◽  
Gas Phase Ions ◽  
Conventional Structure ◽  
Precursor Molecules ◽  
Isotopic Labelling Experiments ◽  
Good Agreement ◽  
Abinitio Calculations

The title ions have been generated by dissociative ionisation of appropriate precursor molecules and have been unequivocally identified by collisional activation and collisional ionisation mass spectrometry. Their heats of formation, [Formula: see text], have been measured and were found to be similar to those for their ionic isomer of conventional structure, [CH3X]+•. The exception is [CH2NH3]+• whose [Formula: see text], is ca. 30 kcal mol−1 higher than that of [CH3NH2]+•. The shapes and appearance energies of metastable peaks in conjunction with isotopic labelling experiments, show that these novel ions do not interconvert with their conventional isomer at internal energies below the threshold for their fragmentation of lowest energy requirement, namely, loss of H•. However, unimolecular H• loss from all [CH2XH]+• ions is preceded by a rate determining isomerisation to [CH3X]+•, followed by fast dissociation. The results are generally in good agreement with recent abinitio calculations. Also described are the properties of the homologous ion [CH2CH2NH3]+•.

scholarly journals A Boron-Boron Double Transborylation Strategy for the Synthesis of gem-Diborylalkanes

2020 ◽  
Author(s):  
Jamie Docherty ◽  
Kieran Nicholson ◽  
Andrew P Dominey ◽  
Stephen Thomas
Keyword(s):  
Transition State ◽  
Thermodynamic Parameters ◽  
Terminal Alkynes ◽  
Isotopic Labelling ◽  
Wide Range ◽  
Boronic Esters ◽  
Isotopic Labelling Experiments

9-Borabicyclo[3.3.1]nonane (H-<i>B</i>-9-BBN) has been used as a catalyst for the sequential double hydroboration of alkynes with pinacolborane (HBpin) to give alkyl gem-di-pinacol boronic esters. This strategy, which is effective for a wide range of terminal alkynes, is predicated upon a key C(<i>sp</i><sup>3</sup>)-B / B-H transborylation reaction. Transition-state thermodynamic parameters and 10-boron-isotopic labelling experiments are indicative of an <i>σ</i>-bond metathesis exchange pathway.

Sign in / Sign up

Export Citation Format

Share Document