Metabolite‐mediated catalyst conversion of PFK and PFP: a mechanism of enyme regulation in green plants

Abstract

Metabolites known to occur in the cytosol of photosynthetic leaf cells were found to mediate the reversible conversion of pyrophosphate-D-fructose-6-phosphate I-phosphotransferase (PFP) to phosphofructokinase (PFK) in partially purified preparations from spinach leaves. Preincubation of PFP with fructose 2,6-bisphosphate, ATP or fructose 6-phosphate converted PFP to PFK. The reverse reaction (PFK + PFP) was promoted by UDP-glucose plus pyrophosphate. These conversions in catalytic capability were accompanied by changes in molecular mass and charge. The results are in accord with the view that the alterations in PFP and PFK activity, provisionally called 'metabolite-mediated catalyst conversion', represent a regulatory mechanism to direct left cytosolic carbon flux in either the biosynthetic or degradatory direction. FPLC Phosphofructokinase Metabolite-mediated catalyst conversion Pyrophosphate-D-fructose-&phosphate I-phosphotransferase

Different Physiological Roles of ATP- and PPi-Dependent Phosphofructokinase Isoenzymes in the Methylotrophic ActinomyceteAmycolatopsis methanolica

“…ATP-PFK and PP i -PFK isoenzymes had previously been reported only in higher plants (5). The two PFK isoenzymes differ in subunit composition and native molecular mass: the ATP-PFK is a dimer with 50-kDa subunits, whereas the PP i -PFK is a tetramer with 43-kDa subunits.…”

A novel pyrophosphate fructose‐6‐phosphate 1‐phosphotransferase from carrot roots Relation to PFK from the same source

“…As a result of our interest in PFP and PFK [8], we decided to purify and characterize these enzymes from the same source and because of the relatively greater stability of PFK in that tissue, carrot roots were selected as source material. Last year, we described pertinent properties of homogeneous cytosolic PKF from carrot roots and showed it to be distinct from PFP [9].…”

“…The column profiles revealed no significant changes in (i) state of association/dissociation or (ii) ratio of forward to reverse activity as a result of treatment with Fru-2,6-P2 (1 and 10 /IM) and PPi (10 mM) (not shown). The absence of such changes distinguishes the carrot root enzyme from its counterpart studied from pea seed [16], spinach leaf [8] and potato tuber [18].…”

“…The apparent conversion of PFP to PFK observed previously [8] is concluded to be due to the metabolite-dependent interconversion of different enzyme forms now known to exist for PFK [14] that was present together with PFP in the earlier preparations. In other words, in our earlier work, we observed interconversion between the different forms of PFK rather than the presumed conversion of PFP to PFK.…”

Characterization and phylogeny of the pfp gene of Amycolatopsis methanolica encoding PPi-dependent phosphofructokinase

“…This class of PP i -PFK is characterized by a low K m for fructose-6-phosphate and an acidic pH optimum for the phosphorylation of fructose-6-phosphate. In plants, PP i -PFK is present as a heterotetrameric enzyme composed of two nonidentical subunits with molecular masses of 60 and 65 kDa (3). As with the yeast and mammalian enzymes, the activity of the plant PP i -PFK is regulated by fructose-2,6-bisphosphate, the K m for fructose-6-phosphate is high, and the enzyme has a neutral pH optimum for the glycolytic reaction.…”