Glucokinase and Fructokinase of Trichomonas vaginalis and Tritrichomonas foetus

ABSTRACT. Trichomonas vaginalis and Tritrichomonas foetus contain glucokinase and not a hexokinase of broad hexose specificity. Tritrichomonas foetus also contains a specific fructokinase which could be resolved from glucokinase by anion exchange chromatography. Native T. vaginalis glucokinase had a Mr of 76,000, and SDS-PAG electrophoresis showed two equally stained bands corresponding to Mr 40,000 and 38,000. Glucose and ATP were by far the best substrates for both trichomonad glucokinases, with Km values as low as 33–35 μM and 75–83 μM, respectively. Substrate saturation curves for these enzymes were all hyperbolic. Tritrichomonas foetus fructokinase required fructose and ATP, with Km values of 200 μM and 81 μM. None of the activities was affected by a number of potential regulatory metabolites, including glucose-6-phosphate. The only exception was AMP which in supraphysiological concentrations had an inhibitory effect on T. foetus fructokinase. In conclusion, the absence of regulation at the hexose phosphorylation step described here, as well as the presence of an easily reversible PPi: fructose-6-phosphate 1 -phosphotransferase described previously (Mertens, E., Van Schaftingen, E. & Müller, M. 1989. Mol. Biochem. Parasitol. , 37 :183–190), suggest that the rate of the 1st part of glycolysis in trichomonads is controlled only by the intracellular availability of hexoses.     

Silencing of FOXO6 inhibits the proliferation,invasion, and glycolysis in colorectal cancer cells

Forkhead box class O6 (FOXO6) is an important member of FOXO family, which has been demonstrated to be implicated in tumor development. However, the role of FOXO6 in colorectal cancer (CRC) is still unclear. The study aimed to investigate the potential roles of FOXO6 in the development of CRC. Our results showed that FOXO6 was overexpressed in CRC tissues and cell lines. FOXO6 knockdown inhibited cell proliferation, as well as repressed the migration and invasion of CRC cells. Additionally, we found that FOXO6 knockdown altered cellular metabolism by inhibiting glycolysis and promoting mitochondrial respiration. Furthermore, FOXO6 knockdown inhibited the activation of PI3K/Akt/mTOR pathway in CRC cells. The results herein indicated that FOXO6 knockdown inhibited cell proliferation, migration, invasion, and glycolysis in CRC cells. PI3K/Akt/mTOR pathway was involved in the effects of FOXO6 on CRC cells. These findings suggested that FOXO6 might be a potential target for the CRC therapy.     

Effect of xiphidiocercarial infection on oxidation of glycolytic and Krebs cycle intermediates in Lymnaea luteola (Mollusca)

With the aim of assessing the effect of xiphidiocercarial infection on its gastropod host, Lymnaea luteola, the oxidation of glycolytic and tricarboxylic acid cycle intermediates by digestive gland homogenates of uninfected and infected snails was studied manometrically. The oxidation of glycolytic and NAD-linked substrates was reduced in infected snails. On the other hand, succinate oxidation was very high in infected snails and the reasons for this are discussed.     

Effect of hypo- and hyperthyroidism on the function and metabolism of macrophages in rats

The effect of thyroid hormones on monocyte migration, phagocytic capacity and hydrogen peroxide production by macrophages and the effect of these hormones on glutamine and glucose metabolism was investigated. The experiments were performed on resident, thioglycollate- and BCG-stimulated cells from hypo- and hyperthyroid rats. High plasma levels of thyroid hormones suppressed the migration of monocytes and hydrogen peroxide production, whereas hypothyuroidism did not affect cell migration but rasied the phagocytic capacity and the hydrogen peroxide production. Hyperthyroidism increased the activities of glutaminase and hexokinase and the rates of decarboxylation of [U-¹⁴C]-glutamine and [U-¹⁴C]-glucose in inflammatory and activated cells. Hypothyroidism stimulated glucose metabolism and had only a slight effect on glutaminolysis. The activity of the TCA cycle was, however, diminished in the presence of high plasma levels of thyroid hormones and enhanced by the hypothyroid state. These findings suggest that the functional changes observed are more likely to be related to the activity of the TCA cycle rather than to glutaminolysis and glycolysis.     

An overview of structure,function, and regulation of pyruvate kinases

In the last step of glycolysis Pyruvate kinase catalyzes the irreversible conversion of ADP and phosphoenolpyruvate to ATP and pyruvic acid, both crucial for cellular metabolism. Thus pyruvate kinase plays a key role in controlling the metabolic flux and ATP production. The hallmark of the activity of different pyruvate kinases is their tight modulation by a variety of mechanisms including the use of a large number of physiological allosteric effectors in addition to their homotropic regulation by phosphoenolpyruvate. Binding of effectors signals precise and orchestrated movements in selected areas of the protein structure that alter the catalytic action of these evolutionarily conserved enzymes with remarkably conserved architecture and sequences. While the diverse nature of the allosteric effectors has been discussed in the literature, the structural basis of their regulatory effects is still not well understood because of the lack of data representing conformations in various activation states. Results of recent studies on pyruvate kinases of different families suggest that members of evolutionarily related families follow somewhat conserved allosteric strategies but evolutionarily distant members adopt different strategies. Here we review the structure and allosteric properties of pyruvate kinases of different families for which structural data are available.     

Intérêt de la TEP/TDM au 18F-FDG dans la neurofibromatose de type 1, expérience du centre national de référence Henri-Mondor sur 10 ans

ObjectiveMalignant peripherals nerve sheath tumours (MPNST) are one of the leading causes of death in neurofibromatosis type 1 (NF1). Given the temporal and spatial multiplicity of suspicious lesions, the histological diagnosis of certainty might require iterative and decaying surgical procedure. Our objective was to determine the threshold values of metabolic metrics determined on ¹⁸F-FDG PET/CT (SUV_max, total lesion glycolysis [TLG], total metabolic tumour volume [TMTV], tumour-to-liver [T/L] ratio and heterogeneity index [HI]) in order to distinguish at best MPNST from benign lesion (simple neurofibromas [NF] or dysplastic NF).Patients and methodsHundred and seven patients from the national reference centre of NF1 Henri-Mondor, clinically suspects of TMGN, underwent 160 ¹⁸F-FDG PET/CT over a period of 10 years, between 2005 and 2015. The hypermetabolics lesions identified on ¹⁸F-FDG PET/CT were confronted with pathological analysis or clinico-radiological and metabolic follow-up of more than 6 months.ResultsFour hundred and eight hypermetabolics lesions were identified, of which 112 were histologically confronted with 38 simple NF, 29 dysplastic NF, 39 TMGN and 6 incidentalomas. The remaining 296 hypermetabolics lesions experienced a median follow-up of 40.4 months [13.5–137 months]. The optimal cut-off values for malignant lesions, determined by ROC curves, were in order of decreasing performance: T/L ratio > 2.03 (sensitivity 96%, specificity 88%); SUVmax > 4.74 (sensitivity 93%, specificity 86%); TLG > 172 (sensitivity 84%, specificity 76%); TMTV > 53.5 (sensitivity 83%, specificity 68%); HI > 1.63 (sensitivity 84%, specificity 54%).Conclusions¹⁸F-FDG PET/CT is a powerful diagnostic and prognostic tool in the management of TMGN. Metabolic metrics allow with good sensitivity and specificity to identify lesions transformed into TMGN. The advent of PET/MRI will undoubtedly allow in the near future to reinforce the diagnostic and prognostic performances for the detection of transformations of neurofibromas in TMGN.     

代谢工程改造异养微生物固定CO2研究进展

环境保护和能源供应是人类关心的两大问题。能源消耗释放出的温室气体对环境造成了严重影响。利用CO_2固定途径可将CO_2转化成燃料或化学品。天然固碳生物通常存在生长缓慢、固碳效率低等问题。通过在模式微生物中增强或重构CO_2固定途径,实现CO_2的再循环,可提高燃料或化学品的产量,减少温室气体排放。文中详细介绍了通过代谢工程手段改造CO_2固定途径改善化学品生产以及糖合成,阐述了相关代谢途径及其中的关键酶在CO_2固定中的作用,介绍了电生化合成系统的应用,显示出CO_2固定的巨大潜力,并展望了未来CO_2固定的研究方向。     

The tumor suppressor WW domain-containing oxidoreductase modulates cell metabolism

The WW domain-containing oxidoreductase (WWOX) encodes a tumor suppressor that is frequently altered in cancer. WWOX binds several proteins and thus is postulated to be involved in a variety of cellular processes. Interestingly, Wwox-knockout mice develop normally in utero but succumb to hypoglycemia and other metabolic defects early in life resulting in their death by 3–4 weeks of age. Cumulative evidence has linked WWOX with cellular metabolism including steroid metabolism, high-density lipoprotein cholesterol (HDL-C) metabolism, bone metabolism and, more recently, glucose metabolism. In this review, we discuss these evolving functions for WWOX and how its deletion affects cellular metabolism and neoplastic progression.     

The SUMO‐E3 ligase PIAS3 targets pyruvate kinase M2

Pyruvate kinase M2 (M2‐PK) controls the rate‐limiting step at the end of the glycolytic pathway in normal proliferating and tumor cells. Other functions of M2‐PK in addition to its role in glycolysis are little understood. The aim of this study was to identify new cellular interaction partners of M2‐PK in order to discover novel links between M2‐PK and cellular functions. Here we show that the SUMO‐E3 ligase protein PIAS3 (inhibitor of activated STAT3) physically interacts with M2‐PK and its isoenzyme M1‐PK. Moreover, we demonstrate that endogenous SUMO‐1‐M2‐PK conjugates exist in mammalian cells. Furthermore, we show that transient expression of PIAS3 but not the RING domain mutant PIAS3 (C299S, H301A) is consistent with nuclear localization of M2‐PK and PIAS3 and M2‐PK partially co‐localize in the nucleus of these cells. This study suggests a link between PIAS3 and nuclear pyruvate kinase. J. Cell. Biochem. 107: 293–302, 2009. © 2009 Wiley‐Liss, Inc.     

Crystal structure of phosphoglucose isomerase from Trypanosoma brucei complexed with glucose-6-phosphate at 1.6 A resolution

Enzymes of glycolysis in Trypanosoma brucei have been identified as potential drug targets for African sleeping sickness because glycolysis is the only source of ATP for the bloodstream form of this parasite. Several inhibitors were previously reported to bind preferentially to trypanosomal phosphoglucose isomerase (PGI, the second enzyme in glycolysis) than to mammalian PGIs, which suggests that PGI might make a good target for species-specific drug design. Herein, we report recombinant expression, purification, crystallization and X-ray crystal structure determination of T. brucei PGI. One structure solved at 1.6 A resolution contains a substrate, D-glucose-6-phosphate, in an extended conformation in the active site. A second structure solved at 1.9 A resolution contains a citrate molecule in the active site. The structures are compared with the crystal structures of PGI from humans and from Leishmania mexicana. The availability of recombinant tPGI and its first high-resolution crystal structures are initial steps in considering this enzyme as a potential drug target.