PLANT PHYSIOLOGY , Vol 101, Issue 3 765-771, Copyright © 1993 by American Society of Plant Biologists
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METABOLISM AND ENZYMOLOGY |
Essential Arginyl Residue at the Active Site of Pyrophosphate:Fructose 6-Phosphate 1-Phosphotransferase from Potato (Solanum tuberosum) Tuber
P. Montavon and N. J. Kruger
Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom
The aim of this work was to test the proposal that the active site of
pyrophosphate:fructose 6-phosphate 1-phosphotransferase (PFP) contains an
essential arginyl residue. Enzyme activity was inhibited equally in the
glycolytic and gluconeogenic directions by arginine-modifying reagents. The
second-order rate constants for 2,3-butanedione and phenylglyoxal were 13.1
[plus or minus] 0.45 and 55.3 [plus or minus] 1.3 M-1 min-1, respectively.
The corresponding values for the kinetic order of inactivation by these
modifying reagents were 0.84 [plus or minus] 0.049 for 2,3-butanedione and
0.89 [plus or minus] 0.052 for phenylglyoxal. The substrates, fructose
6-phosphate and pyrophosphate, and a range of substrate analogs protected
the enzyme from inactivation by 2,3-butanedione. These data suggest that
modification of no more than one arginyl residue at, or close to, the
active site is required to inhibit the enzyme. This result supports the
proposal that the active site of PFP in plants is equivalent to that of the
bacterial ATP-phosphofructokinase (S.M. Carlisle, S.D. Blakeley, S.M.
Hemmingsen, S.J. Trevanion, T. Hiyoshi, N.J. Kruger, and D.T. Dennis [1990]
J Biol Chem 265: 18366-18371).