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ARS Home » Midwest Area » Columbia, Missouri » Plant Genetics Research » Research » Publications at this Location » Publication #179097
Title: EXPRESSION AND PARTIAL CHARACTERIZATION OF BARLEY HOMOGENTISIC ACID GERANYLGERANYL DIPHOSPHATE TRANSFERASE

Author
item HUNTER, SARAH
item CAHOON, EDGAR

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/18/2005
Publication Date: 3/18/2005
Citation: Hunter, S.C., Cahoon, E.B. 2005. Expression and partial characterization of barley homogentisic acid geranylgeranyl diphosphate transferase [abstract]. 2005 Midwest American Society of Plant Biologists Sectional Meeting. p. 66.

Interpretive Summary:

Technical Abstract: Tocotrienols and tocopherols, both vitamin E compounds, consist of an aromatic head group and a lipophilic tail. Both are antioxidants and are an important component of human diets. While tocopherols have a saturated lipid tail derived from phytyl diphosphate (PDP), the lipid tail of a tocotrienol is derived from geranylgeranyl diphosphate (GGDP) and is polyunsaturated. The first committed step of vitamin E biosynthesis is the condensation of homogentisic acid with a prenyl diphosphate. Tocotrienols are found mainly in monocot seeds, while tocopherols are the principle vitamin E found in leaves and most dicot seeds. Two prenyltransferase genes, homogentisic acid geranylgeranyl diphosphate transferase from barley endosperm (HvHGGT) and homogentisic acid phytyl diphosphate transferase from A. thaliana (AtHPT), have been separately expressed in Sf-21 insect cells. Prenyltransferase activity has been assayed using membrane-enriched extracts from insect cells expressing HvHGGT, AtHPT, or uninfected cells (as a control). Using extract from insect cells expressing HvHGGT, the relative activity for GGDP was four-fold higher than with PDP. In contrast, extract from insect cells expressing AtHPT had approximately a 50- to 80-fold preference for PDP over GGPP. No activity with extract from uninfected insect cells was detected. No prenyltransferase activity was detected with solanesyl diphosphate as a donor in any assays. These results demonstrate that HvHGGT and AtHPT are biochemically distinct enzymes.