PLANT PHYSIOLOGY , Vol 111, Issue 4 1153-1159, Copyright © 1996 by American Society of Plant Biologists
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BIOCHEMISTRY AND ENZYMOLOGY |
Hydroxycinnamoyltransferases Involved in the Accumulation of Caffeic Acid Esters in Gametophytes and Sporophytes of Equisetum arvense
M. Hohlfeld, M. Veit and D. Strack
Institut fur Pflanzenbiochemie, Abteilung Sekundarstoffwechsel, Weinberg 3, D-06120 Halle (Saale), Germany (M.H., D.S.)
Four hydroxycinnamoyltransferases from Equisetum arvense L. were studied
that catalyze the formation of mono-O-caffeoyl-meso-tartrate,
di-O-caffeoyl-meso-tartrate, 5-O-caffeoylshikimate (dactylifrate), and
5-O-caffeoylquinate (chlorogenate). The enzymes were classified as coenzyme
A (CoA)-ester-dependent acyltransferases (EC 2.3.1), i.e.
hydroxycinnamoyl-CoA:meso-tartrate hydroxycinnamoyltransferase (CTT),
hydroxycinnamoyl-CoA:caf-feoyl-meso-tartrate hydroxycinnamoyltransferase
(CCT), hydroxycinnamoyl-CoA:shikimate hydroxycinnamoyltransferase (CST),
and hydroxycinnamoyl-CoA:quinate hydroxycinnamoyltransferase. The CTT, CCT,
and CST were partially purified and separated from E. arvense gametophytes
by hydrophobic interaction chromatography on Fractogel TSK Butyl-650
followed by molecular exclusion on fast protein liquid
chromatography-Superdex-75 with 87-, 62-, and 130- fold enrichments and 12,
8, and 11% yields, respectively. The enzyme activities obtained with
caffeoyl-CoA were 95 (CTT), 74 (CCT), and 200 [mu]kat (CST) kg-1 protein.
The apparent native relative molecular weight values were found to be
approximately 45,000 (CTT), 52,000 (CCT), and 50,000 (CST). Each enzyme
showed highest activities at pH 7.5, the CCT and CST in Tris-HCl (1.2 and
1.0 M) and the CTT in imidazole-HCl (1.25 M). Enzyme activities were
stimulated more than 3-fold by 100 mM ascorbate. The apparent energies of
activation (kilojoules mol-1) were calculated to be 56 (CTT), 69 (CST), and
76 (CCT). The enzymes accepted cinnamoyl-CoA and various
hydroxycinnamoyl-CoAs. The time course of the transferase activities along
with that of a fourth one, hydroxycinnamoyl-CoA:quinate
hydroxycinnamoyltransferase, and the pattern of product accumulation were
determined during a 1-year growth period of the E. arvense sporophytes.