Dataset Information

Conversion of Aldehyde to Alkane by a Peroxoiron(III) Complex: A Functional Model for the Cyanobacterial Aldehyde-Deformylating Oxygenase.

ABSTRACT: Cyanobacterial aldehyde-deformylating oxygenase (cADO) converts long-chain fatty aldehydes to alkanes via a proposed diferric-peroxo intermediate that carries out the oxidative deformylation of the substrate. Herein, we report that the synthetic iron(III)-peroxo complex [Fe(III)(?(2)-O2)(TMC)](+) (TMC = tetramethylcyclam) causes a similar transformation in the presence of a suitable H atom donor, thus serving as a functional model for cADO. Mechanistic studies suggest that the H atom donor can intercept the incipient alkyl radical formed in the oxidative deformylation step in competition with the oxygen rebound step typically used by most oxygenases for forming C-O bonds.

SUBMITTER: Shokri A

PROVIDER: S-EPMC4722334 | biostudies-literature | 2015 Jun

REPOSITORIES: biostudies-literature

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Publications

Conversion of Aldehyde to Alkane by a Peroxoiron(III) Complex: A Functional Model for the Cyanobacterial Aldehyde-Deformylating Oxygenase.

Shokri Alireza A Que Lawrence L

Journal of the American Chemical Society 20150610 24

Cyanobacterial aldehyde-deformylating oxygenase (cADO) converts long-chain fatty aldehydes to alkanes via a proposed diferric-peroxo intermediate that carries out the oxidative deformylation of the substrate. Herein, we report that the synthetic iron(III)-peroxo complex [Fe(III)(η(2)-O2)(TMC)](+) (TMC = tetramethylcyclam) causes a similar transformation in the presence of a suitable H atom donor, thus serving as a functional model for cADO. Mechanistic studies suggest that the H atom donor can i ...[more]

PMID: 26030345

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Project description:BackgroundAldehyde-deformylating oxygenase (ADO) is an important enzyme involved in the biosynthetic pathway of fatty alk(a/e)nes in cyanobacteria. However, ADO exhibits quite low chain-length specificity with respect to the substrates ranging from C4 to C18 aldehydes, which is not suitable for producing fuels with different properties or different chain lengths.ResultsBased on the crystal structures of cADOs (cyanobacterial ADO) with substrate analogs bound, some amino acids affecting the substrate specificity of cADO were identified, including the amino acids close to the aldehyde group and the hydrophobic tail of the substrate and those along the substrate channel. Using site-directed mutagenesis, selected amino acids were replaced with bulky ones introducing steric hindrance to the binding pocket via large functional groups. All mutants were overexpressed, purified and kinetically characterized. All mutants, except F87Y, displayed dramatically reduced activity towards C14,16,18 aldehydes. Notably, the substrate preferences of some mutants towards different chain-length substrates were enhanced: I24Y for n-heptanal, I27F for n-decanal and n-dodecanal, V28F for n-dodecanal, F87Y for n-decanal, C70F for n-hexanal, A118F for n-butanal, A121F for C4,6,7 aldehydes, V184F for n-dodecanal and n-decanal, M193Y for C6-10 aldehydes and L198F for C7-10 aldehydes. The impact of the engineered cADO mutants on the change of the hydrocarbon profile was demonstrated by co-expressing acyl-ACP thioesterase BTE, fadD and V184F in E. coli, showing that n-undecane was the main fatty alkane.ConclusionsSome amino acids, which can control the chain-length selectivity of substrates of cADO, were identified. The substrate specificities of cADO were successfully changed through structure-guided protein engineering, and some mutants displayed different chain-length preference. The in vivo experiments of V184F in genetically engineered E. coli proved the importance of engineered cADOs on the distribution of the fatty alkane profile. The results would be helpful for the production of fatty alk(a/e)nes in cyanobacteria with different properties.

Dataset Information

Conversion of Aldehyde to Alkane by a Peroxoiron(III) Complex: A Functional Model for the Cyanobacterial Aldehyde-Deformylating Oxygenase.

Publications

Conversion of Aldehyde to Alkane by a Peroxoiron(III) Complex: A Functional Model for the Cyanobacterial Aldehyde-Deformylating Oxygenase.

Similar Datasets

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