Molecular modeling of manganese regulation of calmodulin-sensitive adenylyl cyclase from mammalian sperm

William A Toscano, John S. Toscano, Diane G. Toscano, Mary K. Gross

Research output: Contribution to journalArticle

2 Scopus citations

Abstract

The soluble calmodulin-sensitive isoform of adenylyl cyclase isolated from equine sperm is unique because it requires Mn2+ rather than Mg 2+ for activity. To gain insight into the molecular action of metals on sperm adenylyl cyclase, the kinetics of Mn2+ and ATP effect was examined. A biphasic response to increases in ATP concentration was observed when metal was held constant. When [Mn2+] exceeded [ATP], however, greatly enhanced enzyme activity was observed. The kinetic profiles were consistent with allosteric activation of adenylyl cyclase by Mn2+. Linear transformation of the data yielded an apparent Km for Mn-ATP of 5.8mM and calculated Vmax of 12nmol cyclic AMP formed/min/mg. Data analysis using calculated equilibrium concentrations of free and complexed reactants provided similar estimates of these kinetic parameters.

Original languageEnglish (US)
Pages (from-to)91-96
Number of pages6
JournalBiochemical and Biophysical Research Communications
Volume312
Issue number1
DOIs
StatePublished - Dec 5 2003

Keywords

  • Allostery
  • Cyclic nucleotides
  • Fertility
  • Kinetics
  • Metal ions
  • Molecular modeling
  • Signal transduction
  • Sperm motility

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