Sodium ions activated phosphofructokinase leading to enhanced D-lactic acid production by Sporolactobacillus inulinus using sodium hydroxide as a neutralizing agent.

Sporolactobacillus inulinus is a superior D-lactic acid-producing bacterium and proposed species for industrial production. The major pathway for D-lactic acid biosynthesis, glycolysis, is mainly regulated via the two irreversible steps catalyzed by the allosteric enzymes, phosphofructokinase (PFK) and pyruvate kinase. The activity level of PFK was significantly consistent with the cell growth and D-lactic acid production, indicating its vital role in control and regulation of glycolysis. In this study, the ATP-dependent PFK from S. inulinus was expressed in Escherichia coli and purified to homogeneity. The PFK was allosterically activated by both GDP and ADP and inhibited by phosphoenolpyruvate; the addition of activators could partly relieve the inhibition by phosphoenolpyruvate. Furthermore, monovalent cations could enhance the activity, and Na+ was the most efficient one. Considering this kind activation, NaOH was investigated as the neutralizer instead of the traditional neutralizer CaCO3. In the early growth stage, the significant accelerated glucose consumption was achieved in the NaOH case probably for the enhanced activity of Na+-activated PFK. Using NaOH as the neutralizer at pH 6.5, the fermentation time was greatly shortened about 22 h; simultaneously, the glucose consumption rate and the D-lactic acid productivity were increased by 34 and 17%, respectively. This probably contributed to the increased pH and Na+-promoted activity of PFK. Thus, fermentations by S. inulinus using the NaOH neutralizer provide a green and highly efficient D-lactic acid production with easy subsequent purification.

Modulation of phosphofructokinase (PFK) from Setaria cervi, a bovine filarial parasite, by different effectors and its interaction with some antifilarials.

BACKGROUND: Phosphofructokinase (ATP: D-fructose-6-phosphate-1-phosphotransferase, EC 2.7.1.11, PFK) is of primary importance in the regulation of glycolytic flux. This enzyme has been extensively studied from mammalian sources but relatively less attention has been paid towards its characterization from filarial parasites. Furthermore, the information about the response of filarial PFK towards the anthelmintics/antifilarial compounds is lacking. In view of these facts, PFK from Setaria cervi, a bovine filarial parasite having similarity with that of human filarial worms, was isolated, purified and characterized. RESULTS: The S. cervi PFK was cytosolic in nature. The adult parasites (both female and male) contained more enzyme activity than the microfilarial (Mf) stage of S. cervi, which exhibited only 20% of total activity. The S. cervi PFK could be modulated by different nucleotides and the response of enzyme to these nucleotides was dependent on the concentrations of substrates (F-6-P and ATP). The enzyme possessed wide specificity towards utilization of the nucleotides as phosphate group donors. S. cervi PFK showed the presence of thiol group(s) at the active site of the enzyme, which could be protected from inhibitory action of para-chloromercuribenzoate (p-CMB) up to about 76% by pretreatment with cysteine or ß-ME. The sensitivity of PFK from S. cervi towards antifilarials/anthelmintics was comparatively higher than that of mammalian PFK. With suramin, the Ki value for rat liver PFK was 40 times higher than PFK from S. cervi. CONCLUSIONS: The results indicate that the activity of filarial PFK may be modified by different effectors (such as nucleotides, thiol group reactants and anthelmintics) in filarial worms depending on the presence of varying concentrations of substrates (F-6-P and ATP) in the cellular milieu. It may possess thiol group at its active site responsible for catalysis. Relatively, 40 times higher sensitivity of filarial PFK towards suramin as compared to the analogous enzyme from the mammalian system indicates that this enzyme could be exploited as a potential chemotherapeutic target against filariasis.

[Cloning, expression and elementary characterization of phosphofructokinase from Bacillus sphaericus C3-41].

OBJECTIVE: Bacillus sphaericus is unable to use hexose and pentoses as the sole carbon source, due to the lack of key enzymes in Embden-Meyerhof-Parnas pathway (EMP), Hexose Monophophate Pathway (HMP) and Entner-Doudoroff (ED) pathway, such as phosphofructokinase (PFK). Based on the genome sequence annotation results of B. sphaericus C3-41, the phosphofructokinase gene pfk was verified with a single copy on chromosome, the aim of this research is to analysis the EMP pathway in B. sphaericus further, and confirm the function of phosphofructokinase. METHODS: The methods of southern-blot of pfk gene among different B. sphaericus strains, pfk ORF cloning from C3-41 and expressing in Escherichia coli, the corresponding sequence analysis and anlignment were used. RESULTS: The pfk ORF of B. sphaericus was composed of 960 bp nucleitides encoding a protein about 42 kDa, and the PFK sequence analysis showed it had the conservative amino acids-binding sites and an ATP-binding domain. The expression of pfk in recombinant E. coli strain could complement the PFK activity of a pfk mutated E. coli strain DF1020. CONCLUSION: The expressed PFK had the conventional phosphofructokinase activity, and settled the foundation for the further research of catabolism of B. sphaericus.

[Isolation and study of active ATP-dependent phosphofructokinase from apple fruits Pyrus domestica Borkh].

The activity of ATP-dependent phosphofructokinase (PFK) from subepidermal tissue of apple fruits was studied. The enzyme extracted under optimal conditions was stable for 14 h at room temperature. The enzyme was partially purified by ammonium sulfate fractionation and dialysis. PFK from apple fruits was found to be ATP-, UTP-, and CTP-specific. It was inhibited by PEP, Gly-2-P, Gly-1,3-DP, and ADP. The effect of the listed inhibitors was diminished by the presence of phosphate. The activity of PFK was stimulated by magnesium cations. The activity of the enzyme in fruits of an Antonovka cultivar was higher than in the Simirenko rennet cultivar by a factor of 1.3.

Phosphofructokinase from muscle of the marine giant barnacle Austromegabalanus psittacus: kinetic characterization and effect of in vitro phosphorylation.

The kinetic properties of phosphofructokinase from muscle of the giant cirripede Austromegabalanus psittacus were characterized, after partial purification by ion exchange chromatography on DEAE-cellulose. This enzyme showed differences regarding PFKs from other marine invertebrates: the affinity for fructose 6-phosphate (Fru 6-P) was very low, with an S(0.5) of 22.6+/-1.4 mM (mean+/-S.D., n=3), and a high cooperativity (n(H) of 2.90+/-0.21; mean+/-S.D., n=3). The barnacle PFK showed hyperbolic saturation kinetics for ATP (apparent K(m ATP)=70 microM, at 5 mM Fru 6-P, in the presence of 2 mM ammonium sulfate). ATP concentrations higher than 1 mM inhibited the enzyme. Ammonium sulfate activated the PFK several folds, increasing the affinity of the enzyme for Fru 6-P and V(max). 5'-AMP (0.2 mM) increased the affinity for Fru 6-P (S(0.5) of 6.2 mM). Fructose 2,6-bisphosphate activated the PFK, with a maximal activation at concentrations higher than 2 microM. Citrate reverted the activation of PFK produced by 0.2 mM 5'-AMP (IC(50 citrate)=2.0 mM), producing a higher inhibition than that exerted on other invertebrate PFKs. Barnacle muscular PFK was activated in vitro after exposure to exogenous cyclic-AMP (0.1 mM) as well as by phosphatidylserine (50 microg/ml), indicating a possible control by protein kinase A and a phospholipid dependent protein kinase (PKC). The results suggest a highly regulated enzyme in vivo, by allosteric mechanisms and also by protein phosphorylation.

The dimorphic yeast Yarrowia lipolytica possesses an atypical phosphofructokinase: characterization of the enzyme and its encoding gene.

The phosphofructokinase from the non-conventional yeast Yarrowia lipolytica (YlPfk) was purified to homogeneity, and its encoding gene isolated. YlPfk is an octamer of 869 kDa composed of a single type of subunit, and shows atypical kinetic characteristics. It did not exhibit cooperative kinetics for fructose 6-phosphate (Hill coefficient, h 1.1; S0.5 52 microM), it was inhibited moderately by MgATP (Ki 3.5 mM), and it was strongly inhibited by phosphoenolpyruvate (Ki 61 microM). Fructose 2,6-bisphosphate did not activate the enzyme, and AMP and ADP were also without effect. The gene YlPFK1 has no introns, and encodes a putative protein of 953 aa, with a molecular mass consistent with the subunit size found after purification. Disruption of the gene abolished growth in glucose and Pfk activity, while reintroduction of the gene restored both properties. This indicates that Y. lipolytica has only one gene encoding Pfk, and supports the finding that the enzyme consists of identical subunits. Glucose did not interfere with growth of the Ylpfk1 disruptant in permissive carbon sources. The unusual kinetic characteristics of YlPfk, and the intracellular concentrations of glycolytic intermediates during growth in glucose, suggest that YlPfk may play an important role in the regulation of glucose metabolism in Y. lipolytica, different from the role played by the enzyme in Saccharomyces cerevisiae.

Expression, purification, crystallization and preliminary crystallographic analysis of Trypanosoma brucei phosphofructokinase.

Phosphofructokinase from Trypanosoma brucei (TbPFK) was purified from a recombinant expression system in Escherichia coli by metal-affinity chromatography via its N-terminal His tag. The yield was 15-20 mg of pure enzyme per litre of culture. M(r) was shown to be 55 585 by mass spectrometry. Crystals suitable for X-ray diffraction analysis were obtained by the hanging-drop method of vapour diffusion with sodium formate as the precipitating agent. Monoclinic crystals of the apoenzyme grew within one week, as did orthorhombic crystals of PFK in the presence of enzymic reaction products or an active-site inhibitor. Initial attempts to solve the structure by molecular replacement with bacterial PFK structures as search models proved unrewarding, but a multiple-copy search with a polyalanine model was successful. In addition, heavy-atom soaking with platinum and mercury has yielded derivatives suitable for X-ray diffraction. A combination of the phase information from the molecular-replacement solution and the heavy-atom derivatives should allow structure solution of TbPFK. The availability of this first eukaryotic PFK structure will be of particular significance for structure-based drug design and will also provide important additional structural evidence for the allosteric control of PFK activity.