PLANT PHYSIOLOGY , Vol 114, Issue 2 565-573, Copyright © 1997 by American Society of Plant Biologists
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BIOCHEMISTRY AND ENZYMOLOGY |
Purification and Characterization of Allene Oxide Cyclase from Dry Corn Seeds
J. Ziegler, M. Hamberg, O. Miersch and B. Parthier
Department of Hormone Research, Institute of Plant Biochemistry, Weinberg 3, D-06120 Halle, Germany (J.Z., O.M., B.P.)
Allene oxide cyclase (AOC; EC 5.3.99.6) catalyzes the cyclization of
12,13(S)-epoxy-9(Z),11,15(Z)-octadecatrienoic acid to 12-oxo-
10,15(Z)-phytodienoic acid, the precursor of jasmonic acid (JA). This
soluble enzyme was purified 2000-fold from dry corn (Zea mays L.) kernels
to apparent homogeneity. The dimeric protein has a molecular mass of 47 kD.
Allene oxide cyclase activity was not affected by divalent ions and was not
feedback-regulated by its product, 12-oxo-l0,15(Z)-phytodienoic acid, or by
JA. ([plus or minus])-cis- 12,13-Epoxy-9(Z)-octadecenoic acid, a substrate
analog, strongly inhibited the enzyme, with 50% inhibition at 20 [mu]M.
Modification of the inhibitor, such as methylation of the carboxyl group or
a shift in the position of the epoxy group, abolished the inhibitory
effect, indicating that both structural elements and their position are
essential for binding to AOC. Nonsteroidal anti-inflammatory drugs, which
are often used to interfere with JA biosynthesis, did not influence AOC
activity. The purified enzyme catalyzed the cyclization of
12,13(S)-epoxy-9(Z),11,15(Z)-octadecatrienoic acid derived from linolenic
acid, but not that of 12,13(S)-epoxy-9(Z),11- octadecadienoic acid derived
from linoleic acid.
