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J Biol Chem. 2016 Apr 22;291(17):9052-9. doi: 10.1074/jbc.M115.709154. Epub 2016 Feb 10.

Control of the Position of Oxygen Delivery in Soybean Lipoxygenase-1 by Amino Acid Side Chains within a Gas Migration Channel.

Author information

1
From the Department of Molecular and Cell Biology, Department of Chemistry, and the California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, California 94720.
2
From the Department of Molecular and Cell Biology, Department of Chemistry, and the California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, California 94720 klinman@berkeley.edu.

Abstract

Understanding gas migration pathways is critical to unraveling structure-function relationships in enzymes that process gaseous substrates such as O2, H2, and N2 This work investigates the role of a defined pathway for O2 in regulating the peroxidation of linoleic acid by soybean lipoxygenase 1. Computational and mutagenesis studies provide strong support for a dominant delivery channel that shuttles molecular oxygen to a specific region of the active site, thereby ensuring the regio- and stereospecificity of product. Analysis of reaction kinetics and product distribution in channel mutants also reveals a plasticity to the gas migration pathway. The findings show that a single site mutation (I553W) limits oxygen accessibility to the active site, greatly increasing the fraction of substrate that reacts with oxygen free in solution. They also show how a neighboring site mutation (L496W) can result in a redirection of oxygen toward an alternate position of the substrate, changing the regio- and stereospecificity of peroxidation. The present data indicate that modest changes in a protein scaffold may modulate the access of small gaseous molecules to enzyme-bound substrates.

KEYWORDS:

catalysis; enzyme mechanism; enzyme mutation; kinetics; lipoxygenase; oxygen channel; protein structure; regio- and stereospecificity

PMID:
26867580
PMCID:
PMC4861474
DOI:
10.1074/jbc.M115.709154
[Indexed for MEDLINE]
Free PMC Article

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