Plant Physiol, April 2000, Vol. 122, pp. 1225-1230
Compartmentation of ATP:Citrate Lyase in Plants1
Dhandapani
Rangasamy2 and
Colin
Ratledge*
Department of Biological Sciences, University of Hull, Hull HU6
7RX, United Kingdom
Extracts
prepared from young leaves of Pea (Pisum sativum),
tobacco (Nicotiana tabacum), rape (Brassica
napus), and spinach (Spinacia oleracea) all
contained ATP:citrate lyase (ACL) activity, which was most active in
rape leaflets (130 nmol min
1 g fresh weight). In rape and
spinach, ACL activity was predominantly localized in the plastids
(between about 78% and 90% of the total activity), whereas in pea and
tobacco, distribution was mainly cytosolic (about 85% and 78%,
respectively, of the total). These distributions were calculated from
the relative distributions of plastid and cytosol marker enzymes.
Cross-reactivity between plant and rat ACL antibody was carried out by
immunoblot analysis and, in rape and spinach, showed that a 120-kD
protein, presumably indicating homomeric ACL proteins, was present in
both cytosolic and plastidic fractions. In pea, two cross-reacting
proteins were detected, the major material being in the cytosol
fraction. Therefore, ACL occurs both in the cytosol and plastids of
higher plants, but the distribution of activity changes according to
the species. The plastidic ACL is proposed to function for the supply
of acetyl-coenzyme A for lipid biosynthesis de novo, whereas the
cytosolic ACL may provide acetyl-coenzyme A for the mevalonate pathway
or fatty acid elongation.
1
D.R. received financial support from the
Commonwealth Scholarship Committee, UK.
2
Present address: Department of Medical
Microbiology, 473A Reynold Medical Building, Texas A&M University,
College Station, TX 77843-1114.
*
Corresponding author; e-mail c.ratledge{at}biosci.hull.ac.uk; fax
44-1482-465458.
© 2000 American Society of Plant Physiologists
