Pyrophosphate‐dependent phosphofructokinase, an anaerobic glycolytic enzyme?

Mertens, Emmanuel

doi:10.1016/0014-5793(91)80711-b

Cited by 156 publications

(110 citation statements)

References 27 publications

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“…PP, levels do not alter detectably during rapid changes in the rate of respiration or when tissues are subjected to anoxia or respiratory poisons (Dancer and ap Rees, 1989;Quick et al, 1989) whereas ATP levels change appreciably under these conditions. Since other PP,-linked enzymes, such as PP, :phosphofructokinase, are induced by anoxia in plants (Mertens et al, 1990), it has been suggested that the coordinate stabilization of PP, levels and operation of the V-PPase and other PP,-dependent enzymes would provide a back-up system for metabolism during anaerobiosis (Mertens, 1991 ;Rea and Poole, 1993). Indeed, the capacity of the V-PPase for primary H i -translocation may confer a double advantage during anaerobiosis.…”

Section: Discussionmentioning

confidence: 99%

Steady‐state kinetics of substrate hydrolysis by vacuolar H⁺‐pyrophosphatase

Baykov

Bakuleva²,

Rea

1993

European Journal of Biochemistry

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The results of analyses of the steady-state kinetics of the vacuolar H+-translocating pyrophosphatase (V-PPase) of native tonoplast vesicles isolated from etiolated hypocotyls of fignu rudiutu (mung bean) and purified enzyme from the same source under a wide range of Mg", pyrophosphate (PPJ and K' concentrations are consistent with a minimal reaction scheme in which dimagnesium pyrophosphate is the active substrate species and catalysis is mediated by preformed enzyme-Mg'+ complex. When account is taken of the sensitivity of the V-PPase to ionic strength, additional kinetic interactions are not required to describe the behavior of the enzyme. N-Ethylmaleimide-protection assays show that the dissociation constant for Mg" binding in the absence of PP, is an order of magnitude smaller than that estimated from the steady-state kinetics of PP, hydrolysis. Two distinct Mg"-binding sites are therefore invoked. Since the protective action of Mg2+ is independent of the nature of the monovalent cation and Mg" and K' do not compete during substrate hydrolysis, divalent and monovalent cations are concluded to bind at separate sites. The pH dependencies of the kinetic parameters are consistent with the participation of groups of pK, 5.7 and 8.6 in substrate binding and groups of pK, 6.1 and 9.0 in the substrate-conversion step, indicating that at least four ionizable groups are essential for catalysis. These findings are discussed with respect to the reaction mechanism of the V-PPase and the potential regulatory significance of cytosolic free Mg2+ and K+ in vivo.Plant cells contain alternative metabolic pathways which utilize nucleotides or inorganic pyrophosphate (PP,) as energy sources. While the full significance of this phenomenon remains to be determined, this pattern of alternate proximate energy sources is exemplified by the presence of two parallel H' pumps in the vacuolar membrane (tonoplast). These are the vacuolar H'-ATPase (V-ATPase), an enzyme common to the endomembranes of all characterized eukaryotes (Nelson, 1992;Sze et al., 1992), and a vacuolar H i -translocating inorganic pyrophosphatase (V-PPase), which is ubiquitous in plants but otherwise known in only a few phototrophic bacteria (Baltscheffsky, 1978;Rea et al., 1992a;Rea and Poole, 1993). Both enzymes catalyze electrogenic H'-translocation from the cytosol to vacuole lumen to establish an inside-acid pH difference (dpH) and inside-positive electrical potential difference ( d w ) which is employed to energize the H+-coupled, secondary transport of solutes across the vacuolar membrane (Sze, 1985 ;Blumwald, 1987 The potential bioenergetic impact of the V-PPase is indicated by its intrinsic catalytic activity and abundance. The enzyme is capable of generating a steady-state transtonoplast H+-electrochemical potential difference (dPH +) of similar, or greater, magnitude than the V-ATPase on the same membrane (Johannes and Felle, 1989;Maeshima and Yoshida, 1989; Pope and Leigh, 1988;Rea et al., 1992b) and abundance estimates indicate the the V-PPase constitu...

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Section: Discussionmentioning

confidence: 99%

Steady‐state kinetics of substrate hydrolysis by vacuolar H⁺‐pyrophosphatase

Baykov

Bakuleva²,

Rea

1993

European Journal of Biochemistry

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“…PFP appears to be an adaptive enzyme whose activity is responsive to environmental stresses, such as Pi nutrition and anaerobiosis, and to developmental or tissue-specific cues (Duff et al, 1989b;Stitt, 1990;Mertens, 1991;Theodorou et al, 1992). Unlike plant PFK, most plant PFPs display potent activation by nanomolar concentrations of the regulatory metabolite Fru-2,6-Pz (Stitt, 1990).…”

Section: Pfp a N Adaptive Enzymementioning

confidence: 99%

“…The PFP of several heterotrophic plant tissues has also been proposed to operate as a glycolytic bypass to PFK during periods of anaerobiosis (Mertens, 1991). The use of PPi rather than ATP could confer a significant energetic advantage to plants subjected to environmental stresses, such as Pi deprivation or anoxia.…”

Section: Pfp a N Adaptive Enzymementioning

confidence: 99%

Metabolic Adaptations of Plant Respiration to Nutritional Phosphate Deprivation

Theodorou¹,

Plaxton²

1993

Plant Physiol.

335

193

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“…In addition, effectors that modulate the activity of PFK in other organisms, such as ATP, citrate, fructose 2,6-bisphosphate and P i , have no effect in Trypanosoma brucei (Michels et al 1997) or Leishmania donovani (Lopez et al 2002). The many differences between the active site of the two classes of PFKs and the striking differences in ligand-binding properties between the human and parasite enzymes suggest great potential for structure-based design of drugs (Mertens 1991, Michels et al 1997). In a previous biochemical characterisation of Trypanosoma cruzi PFK (Aguilar & Urbina 1986), this enzyme was reported to have an apparent molecular mass of 17,000 and a complex kinetic pattern for its interaction with D-F6P.…”

mentioning

confidence: 99%