Mechanistic studies of phosphoenolpyruvate carboxylase from Zea mays utilizing formate as an alternate substrate for bicarbonate.
Formate is an alternate substrate for bicarbonate in the reaction with PEP catalyzed by phosphoenolpyruvate carboxylase from Zea mays, producing formyl phosphate and pyruvate. The Km for formate is 25 +/- 2 mM, and the maximum velocity is 1% of that for bicarbonate at pH 8.0. Use of [18O]formate produces inorganic phosphate containing 1 equiv of 18O, but no label is incorporated into residual phosphoenolpyruvate. PEP carboxylase catalyzes the hydrolysis of phosphoglycolate or L-phospholactate 2000 times more slowly and D-phospholactate 4000 times more slowly than the reaction between bicarbonate and PEP.
Janc
J W
JW
Institute for Enzyme Research, University of Wisconsin, Madison 53705.
Cleland
W W
WW
O'Leary
M H
MH
D001639:Bicarbonates / Q000378:metabolism*; D005561:Formates / Q000378:metabolism*; D006016:Glycolates / Q000378:metabolism; D006358:Hot Temperature; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D010103:Oxygen Isotopes; D010730:Phosphoenolpyruvate Carboxylase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D011773:Pyruvates / Q000378:metabolism; D013379:Substrate Specificity; D003313:Zea mays / Q000201:enzymology*
D001639:Bicarbonates; D005561:Formates; D006016:Glycolates; D010103:Oxygen Isotopes; D011773:Pyruvates; C017092:bromopyruvate; D010744:Phosphoric Monoester Hydrolases; D010730:Phosphoenolpyruvate Carboxylase; C013193:phosphoglycolate