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Hexose Transporters (hexose + transporter)
Selected AbstractsHexose-specificity of hexokinase and ADP-dependence of pyruvate kinase play important roles in the control of monosaccharide utilization in freshly diluted boar spermatozoaMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 9 2006Antonio Medrano Abstract Incubation of boar sperm from fresh ejaculates in a minimal medium with 10 mM glucose induced a fast and intense activation of glycolysis, as indicated by the observed increases in the intracellular levels of glucose 6-phosphate (G 6-P) and ATP and the rate of formation of extracellular L -lactate. The effect of glucose was much more intense than that induced by fructose, sorbitol, and mannose. The greater utilization of glucose was related to a much greater sensitivity to hexokinase when compared with the other monosaccharides. Thus, the presence of 0.5 mM glucose induced total hexokinase activity in supernatants from sperm extracts of 1.7,±,0.1 mIU/mg protein, while the same concentration of both fructose, mannose, and sorbitol induced total hexokinase activity from 0.3,±,0.1 mIU/mg protein to 0.60,±,1 mIU/mg protein. Kinetic analysis of the total pyruvate kinase activity indicated that this activity was greatly dependent on the presence of ADP and also showed a great affinity for PEP, with an estimated Km in supernatants of 0.15,0.20 mM. Immunological location of proteins closely related to glycolysis, like GLUT-3 hexose transporter and hexokinase-I, indicated that these proteins showed the trend to be distributed around or in the cellular membranes of both head and midpiece in a grouped manner. We conclude that glycolysis is regulated by both the specific availability of a concrete sugar and the internal equilibrium between ATP and ADP levels. Furthermore, localization of proteins involved in the control of monosaccharide uptake and phosphorylation suggests that glycolysis starts at concrete points in the boar-sperm surface. Mol. Reprod. Dev. 1179,1194, 2006. © 2006 Wiley-Liss, Inc. [source] Combined phylogenetic and neighbourhood analysis of the hexose transporters and glucose sensors in yeastsFEMS YEAST RESEARCH, Issue 4 2009Margarida Palma Abstract The sugar porter family in yeasts encompasses a wide variety of transporters including the hexose transporters and glucose sensors. We analysed a total of 75 members from both groups in nine hemiascomycetous species, with complete and well-annotated genomes: Saccharomyces cerevisiae, Candida glabrata, Zygosaccharomyces rouxii, Kluyveromyces thermotolerans, Saccharomyces kluyverii, Kluyveromyces lactis, Eremothecium gossypii, Debaryomyces hansenii and Yarrowia lipolytica. We present a model for the evolution of the hexose transporters and glucose sensors, supported by two types of complementary evidences: phylogeny and neighbourhood analysis. Five lineages of evolution were identified and discussed according to different mechanisms of gene evolution: lineage A for HXT1, HXT3, HXT4, HXT5, HXT6 and HXT7; lineage B for HXT2 and HXT10; lineage C for HXT8; lineage D for HXT14; and lineage E for SNF3 and RGT2. [source] The sugar porter gene family of Laccaria bicolor: function in ectomycorrhizal symbiosis and soil-growing hyphaeNEW PHYTOLOGIST, Issue 2 2008Mónica Fajardo López Summary ,,Formation of ectomycorrhizas, a symbiosis with fine roots of woody plants, is one way for soil fungi to overcome carbohydrate limitation in forest ecosystems. ,,Fifteen potential hexose transporter proteins, of which 10 group within three clusters, are encoded in the genome of the ectomycorrhizal model fungus Laccaria bicolor. For 14 of them, transcripts were detectable. ,,When grown in liquid culture, carbon starvation resulted in at least twofold higher transcript abundances for seven genes. Temporarily elevated transcript abundance after sugar addition was observed for three genes. Compared with the extraradical mycelium, ectomycorrhiza formation resulted in a strongly enhanced expression of six genes, of which four revealed their highest observed transcript abundances in symbiosis. A function as hexose importer was proven for three of them. Only three genes, of which just one was expressed at a considerable level, revealed a reduced transcript content in mycorrhizas. ,,From gene expression patterns and import kinetics, the L. bicolor hexose transporters could be divided into two groups: those responsible for uptake of carbohydrates by soil-growing hyphae, for improved carbon nutrition, and to reduce nutrient uptake competition by other soil microorganisms; and those responsible for efficient hexose uptake at the plant,fungus interface. [source] | ||||||||||