Display Settings:

Format

Send to:

Choose Destination
See comment in PubMed Commons below
Plant Physiol. 2002 Jul;129(3):1066-75.

Leucine-derived cyano glucosides in barley.

Author information

  • 1Plant Biochemistry Laboratory, Department of Plant Biology, Royal Veterinary and Agricultural University, Frederiksberg, Copenhagen, Denmark. kani@kvl.dk

Abstract

Barley (Hordeum vulgare) seedlings contain five cyano glucosides derived from the amino acid L-leucine (Leu). The chemical structure and the relative abundance of the cyano glucosides were investigated by liquid chromatography-mass spectrometry and nuclear magnetic resonance analyses using spring barley cultivars with high, medium, and low cyanide potential. The barley cultivars showed a 10-fold difference in their cyano glucoside content, but the relative content of the individual cyano glucosides remained constant. Epiheterodendrin, the only cyanogenic glucoside present, comprised 12% to 18% of the total content of cyano glucosides. It is proposed that the aglycones of all five cyano glucosides are formed by the initial action of a cytochrome P450 enzyme of the CYP79 family converting L-Leu into Z-3-methylbutanal oxime and subsequent action of a less specific CYP71E enzyme converting the oxime into 3-methylbutyro nitrile and mediating subsequent hydroxylations at the alpha-, as well as beta- and gamma-, carbon atoms. Presence of cyano glucosides in the barley seedlings was restricted to leaf tissue, with 99% confined to the epidermis cell layers of the leaf blade. Microsomal preparations from epidermal cells were not able to convert L-[(14)C]Leu into the biosynthetic intermediate, Z-3-methylbutanal-oxime. This was only achieved using microsomal preparations from other cell types in the basal leaf segment, demonstrating translocation of the cyano glucosides to the epidermal cell layers after biosynthesis. A beta-glucosidase able to degrade epiheterodendrin was detected exclusively in yet a third compartment, the endosperm of the germinating seed. Therefore, in barley, a putative function of cyano glucosides in plant defense is not linked to cyanide release.

PMID:
12114561
[PubMed - indexed for MEDLINE]
PMCID:
PMC166501
Free PMC Article
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Write to the Help Desk