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Query: EC:4.1.1.32 (phosphoenolpyruvate carboxykinase)
 4,204 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The aim of this work was to investigate the stereoselectivity of maize leaf phosphoenolpyruvate carboxylase with E- and Z-2-phosphoenolbutyrate as inhibitors and substrates. In addition, a procedure is presented for the separation of the isomers of 2-phosphoenolbutyrate. The method is based on the different interaction of those compounds with a strong anion-exchange high-pressure liquid chromatography column using 50 mM potassium phosphate (pH 3) as elution buffer, and allows the obtention of pure E- and Z-P-enolbutyrate with high yield. The same system was used to identify Z-P-enolbutyrate as the product of the phosphorylation of 2-oxobutyrate by rabbit muscle pyruvate kinase. In the presence of 5 mM Mg2+, both isomers of P-enolbutyrate inhibited C4-plant P-enolpyruvate carboxylase; the values of Ki were 15-20 microM and 100-110 microM for Z- and E-P-enolbutyrate, respectively. With 0.5 mM Mn2+, the Z isomer was also effective as inhibitor (Ki = 35-40 microM), while the E isomer produced activation of the carboxylase probably due to its binding at an allosteric site. Both compounds were substrates of the enzyme with similar V/Km values; however, V and Km for the two isomers were significantly different (i.e. Km = 110 microM for Z-P-enolbutyrate and 220 microM for E-P-enolbutyrate). The results indicate the existence of stereoselectivity for the binding of P-enolbutyrate to the active site of P-enolpyruvate carboxylase. However, this fact does not affect the use of the isomers as substrates by the plant carboxylase.
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PMID:Stereoselectivity of the interaction of E- and Z-2-phosphoenolbutyrate with maize leaf phosphoenolpyruvate carboxylase. 336 12

(Z)-3-(Fluoromethyl)phosphoenolpyruvate has been synthesized in nine chemical steps from glyoxylic acid. The compound is stable at pH 3, but at pH 8 it decomposes within seconds to give 2-oxo-3-butenoate. When 3-(fluoromethyl)phosphoenolpyruvate is added to a solution of phosphoenolpyruvate carboxylase or pyruvate kinase, the enzyme is inactivated over the course of an hour. Identical kinetics of inactivation are observed whether the reaction is initiated by addition of 3-(fluoromethyl)-phosphoenolpyruvate, preformed 2-oxo-3-butenoate, or 4-fluoro-2-oxobutanoate (which rapidly undergoes elimination of fluoride ion to form 2-oxo-3-butenoate). The inactivating species in all cases is believed to be 2-oxo-3-butenoate. The inactivation is completely prevented by the presence of dithiothreitol, which reacts rapidly with 2-oxo-3-butenoate. Studies with competitive inhibitors of both enzymes indicate that inactivation does not occur at the active site.
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PMID:(Z)-3-(fluoromethyl)phosphoenolpyruvate: synthesis and enzymatic studies. 336 90