PLANT PHYSIOLOGY , Vol 101, Issue 2 499-506, Copyright © 1993 by American Society of Plant Biologists
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METABOLISM AND ENZYMOLOGY |
Characterization of Maize Acetyl-Coenzyme A Carboxylase
M. A. Egli, B. G. Gengenbach, J. W. Gronwald, D. A. Somers and D. L. Wyse
Departments of Agronomy and Plant Genetics (M.A.E., B.G.G., D.A.S., D.L.W.) and Plant Biology (B.G.G.), and Plant Molecular Genetics Institute (B.G.G., D.A.S.), University of Minnesota, and Plant Science Research Unit, Agricultural Research Service, United States Department of Agriculture (J.W.G.), St. Paul, Minnesota 55108
Maize (Zea mays L.) leaf acetyl-CoA carboxylase (ACCase) was purified about
500-fold by ammonium sulfate fractionation and gel filtration and blue
Sepharose affinity and anion-exchange chromatography. Most ACCase activity
(85%) recovered from the anion-exchange column was found in a highly
purified fraction (specific activity 5.5 [mu]mol acid-stable product min-1
mg-1) that consisted primarily of a single 227-kD biotinylated polypeptide.
The fraction represented 29% of the original activity and was designated
ACCase I. A second partially purified ACCase activity (ACCase II) eluted
earlier during anion-exchange chromatography, contained a single
biotinylated polypeptide of 219 kD, was poorly recognized by antiserum
raised against the ACCase I polypeptide, and was less inhibited by the
herbicides haloxyfop or sethoxydim than was ACCase I. ACCase I and II both
utilized propionyl-CoA as substrate about 50% as effectively as acetyl-CoA,
and neither utilized methylcrotonyl-CoA. Immunoprecipitation with antiserum
and protein blotting of crude extracts of leaf, embryo, and endosperm
tissue and suspension cells indicated that most ACCase activity in these
tissues was immunologically similar and consisted of ACCase I. Only leaves
contained significant amounts of the ACCase II polypeptide; however, no
ACCase II polypeptide was found in isolated mesophyll chloroplasts. The
ACCase I and II polypeptides appear to be subunits of distinct ACCase
isoforms.
