Hexose-specificity of hexokinase and ADP-dependence of pyruvate kinase play important roles in the control of monosaccharide utilization in freshly diluted boar spermatozoa

Antonio Medrano, Núria García-Gil, Laura Ramió, Ma Montserrat Rivera, Josep Ma Fernández-Novell, Alfredo Ramírez, Alejandro Peña, Ma Dolors Briz, Elisabet Pinart, Ilona I. Concha, Sergi Bonet, Teresa Rigau, Joan E. Rodríguez-Gil

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    22 Citations (Scopus)

    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 mlU/mg protein, while the same concentration of both fructose, mannose, and sorbitol induced total hexokinase activity from 0.3 ± 0.1 mlU/mg protein to 0.60 ± 1 mlU/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-1, 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. © 2006 Wiley-Liss, Inc.
    Original languageEnglish
    Pages (from-to)1179-1194
    JournalMolecular Reproduction and Development
    Volume73
    Issue number9
    DOIs
    Publication statusPublished - 1 Sep 2006

    Keywords

    • Boar spermatozoa
    • Energy metabolism
    • Hexokinase
    • Hexoses
    • Pyruvate kinase

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