Mechanistic studies of phosphoenolpyruvate carboxylase from Zea mays utilizing formate as an alternate substrate for bicarbonate. |
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Authors: | J W Janc W W Cleland M H O'Leary |
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Institution: | Institute for Enzyme Research, University of Wisconsin, Madison 53705. |
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Abstract: | 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. |
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