Carboxylation and dephosphorylation of phosphoenol-3-fluoropyruvate by maize leaf phosphoenolpyruvate carboxylase

Abstract

The analogue (Z)-phosphoenol-3-fluoropyruvate [(Z)-3-fluoro-2-(phosphono-oxy)propenoic acid] was tested as substrate of maize leaf phosphoenolpyruvate carboxylase. Studies with NaH14CO3 indicate that the analogue is carboxylated by the enzyme. However, this reaction accounts for only one-tenth of the activity measured by Pi liberation. The rest of the analogue is merely dephosphorylated. This is the first analogue for which both carboxylation and dephosphorylation have been observed.

Mechanistic studies of phosphoenolpyruvate carboxylase from Zea mays with (Z)- and (E)-3-fluorophosphoenolpyruvate as substrates

“…Consistent with previous reports by Diaz et al (1988) and Gonzalez and Andreo (1988), we find that reaction of F-PEP with PEP carboxylase results in a mixture of F-OAA and F-pyruvate. The (E) isomer gives 86% (S)-3-F-OAA and 14% 3-fluoropyruvate.…”

“…isomer, and the majority of the 14% of F-OAA formed arose therefore from the carboxylation of the (E) isomer. Gonzalez and Andreo (1988) did not comment on the isomeric purity of the F-PEP used in their experiments, but the results presented here allow us to estimate that it contained 8% of the (£) isomer, so that the carboxylation they report is again predominantly the result of carboxylation of the (£) isomer.…”

“…Previous investigations of the substrate activity of predominantly (Z)-F-PEP have reported that carboxylation accounts for 10% (Gonzalez & Andreo, 1988) and 14% (Diaz et al, 1988) of the consumption of F-PEP. The F-PEP used in the experiments of Diaz et al (1988) contained 13% of the (£)…”

“…In addition, F-PEP has been used to determine the stereochemistry of the reaction catalyzed by phosphoenolpyruvate carboxykinase (Hwang & Nowak, 1986). Recently, two independent studies of the substrate activity of F-PEP with maize PEP carboxylase have been reported (Diaz et al, 1988;Gonzalez & Andreo, 1988). Both investigations demonstrated that the primary reaction of F-PEP with PEP carboxylase was hydrolysis, resulting in the formation of 3-fluoropyruvate.…”

Μελετη Του Ενεργου Κεντρου Της Καρβοξυλασης Του Φωσφοενολπυροσταφυλικου Και Τουρολου Των Συνδιαλυτων Στη Δραστηριοτητα Του Ενζυμου Σε Φυσιολογικες Θερμοκρασιες

“…Η συγχρονισμένη κατάλυση είναι συνήθης σε πολλές ενζυμικές αντιδράσεις και προσφέρει πλεονεκτήματα όπως ο περιορισμός της ανάγκης ενδιάμεσων προϊόντων με υψηλή ενέργεια που μειώνουν την ταχύτητα της αντίδρασης και η αποφυγή της απώλειας δραστικών ενδιάμεσων σε μη παραγωγικές αντιδράσεις. Ωστόσο, οι μετέπειτα πειραματικές μελέτες (49,125), ιδιαίτερα δε αυτές με χρησιμοποίηση χημικών αναλόγων του υποστρώματος (27,36,40,41,44), ενισχύουν την υπόθεση του O'Leary (122,123) ότι η αντίδραση περιλαμβάνει δύο στάδια: α) την αποφωσφορυλίωση του φωσφοενολπυροσταφυλικού και β) την καρβοξυλίωση του προς σχηματισμό οξαλοξεικού.…”