From: Robert Coyote (coyyote@hotmail.com)
Date: Fri Feb 22 2002 - 11:48:09 MST
Isnt Citrulline just a metabolic relative of arginine and ornithine?
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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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