From: Doug Skrecky (oberon@vcn.bc.ca)
Date: Fri Feb 22 2002 - 10:53:02 MST
Citrulline, a novel compatible solute in drought-tolerant wild watermelon
leaves, is an efficient hydroxyl radical scavenger
FEBS Letters 508: 438-442 2001
Abstract: Drought-tolerant wild watermelon accumulates high levels of
citrulline in the leaves in response to drought conditions. In this work,
the hydroxyl radical-scavenging activity of citrulline was investigated
in vitro. The second-order rate constant for the reaction between
citrulline and hydroxyl radicals was found to be 3,900,000,000 M-1 s-1,
demonstrating that citrulline is one of the most efficient scavengers
among compatible solutes examined so far. Moreover, citrulline
effectively protected DNA and an enzyme from oxidative injuries. Liquid
chromatography-mass spectrometry analysis revealed that at least four
major products were formed by the reaction between citrulline and
hydroxyl radicals. Activities of metabolic enzymes were not inhibited by
up to 600 mM citrulline, indicating that citrulline does not interfere
with cellular metabolism. We reasoned, from these results, that
citrulline contributes to oxidative stress tolerance under drought
conditions as a novel hydroxyl radical scavenger.
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