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Two-step oxidation of glycerol to glyceric acid catalyzed by the Phanerochaete chrysosporium glyoxal oxidase

Paper ID Volume ID Publish Year Pages File Format Full-Text
17276 42656 2012 8 PDF Available
Title
Two-step oxidation of glycerol to glyceric acid catalyzed by the Phanerochaete chrysosporium glyoxal oxidase
Abstract

Glyoxal oxidase of P. chrysosporium is a radical copper oxidase that catalyzes oxidation of aldehydes to carboxylic acids coupled to dioxygen reduction to H2O2. In addition to known substrates, glycerol is also found to be a substrate for glyoxal oxidase. During enzyme turnover, glyoxal oxidase undergoes a reversible inactivation, probably caused by loss of the active site free radical, resulting in short-lasting enzyme activities and undetectable substrate conversions. Enzyme activity could be extended by including two additional enzymes, horseradish peroxidase and catalase, in addition to a redox chemical activator, such as Mn(III) (or Mn(II) + H2O2) or hexachloroiridate. Using this three-enzyme system glycerol was converted in glyceric acid in a two-step reaction, with glyceraldehyde as intermediate. A possible operation mechanism is proposed in which the three enzymes would work coordinately allowing to maintain a sustained glyoxal oxidase activity. In the course of its catalytic cycle, glyoxal oxidase alternates between two functional and interconvertible reduced and oxidized forms resulting from a two-electron transfer process. However, glyoxal oxidase can also undergo an one-electron reduction to a catalytically inactive form lacking the active site free radical. Horseradish peroxidase could use glyoxal oxidase-generated H2O2 to oxidize Mn(II) to Mn(III) which, in turn, would reoxidize and reactivate the inactive form of glyoxal oxidase. Catalase would remove the excess of H2O2 generated during the reaction. In spite of the improvement achieved using the three-enzyme system, glyoxal oxidase inactivation still occurred, which resulted in low substrate conversions. Possible causes of inactivation, including end-product inhibition, are discussed.

► Glyoxal oxidase of the fungus P. chrysosporium can accept glycerol as substrate. ► Glyoxal oxidase inactivation during enzyme turnover prevents substrate conversion. ► Addition of horseradish peroxidase, catalase and a chemical oxidant partially avoids inactivation. ► The three-enzyme system allows the two-step conversion of glycerol to glyceric acid.

Keywords
Phanerochaete chrysosporium; Glyoxal oxidase; Horseradish peroxidase; Catalase; Glycerol; Glyceric acid
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Two-step oxidation of glycerol to glyceric acid catalyzed by the Phanerochaete chrysosporium glyoxal oxidase
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Publisher
Database: Elsevier - ScienceDirect
Journal: Enzyme and Microbial Technology - Volume 50, Issue 2, 10 February 2012, Pages 143–150
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
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Full-text PDF Download
Online Support
Any Questions? feel free to contact us