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

doi:10.1016/j.bbrc.2003.09.215

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

Environmental Health Sciences

Research output: Contribution to journal › Article › peer-review

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 K_m for Mn-ATP of 5.8mM and calculated V_max 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 language	English (US)
Pages (from-to)	91-96
Number of pages	6
Journal	Biochemical and Biophysical Research Communications
Volume	312
Issue number	1
DOIs	https://doi.org/10.1016/j.bbrc.2003.09.215
State	Published - Dec 5 2003

Bibliographical note

Funding Information:
Supported in part by a grant from NIH: ES-07155.

Keywords

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

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title = "Molecular modeling of manganese regulation of calmodulin-sensitive adenylyl cyclase from mammalian sperm",

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.",

keywords = "Allostery, Cyclic nucleotides, Fertility, Kinetics, Metal ions, Molecular modeling, Signal transduction, Sperm motility",

author = "Toscano, {William A} and Toscano, {John S.} and Toscano, {Diane G.} and Gross, {Mary K.}",

note = "Funding Information: Supported in part by a grant from NIH: ES-07155. ",

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AU - Toscano, William A

AU - Toscano, John S.

AU - Toscano, Diane G.

AU - Gross, Mary K.

N1 - Funding Information: Supported in part by a grant from NIH: ES-07155.

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N2 - 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.

AB - 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.

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KW - Cyclic nucleotides

KW - Fertility

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KW - Metal ions

KW - Molecular modeling

KW - Signal transduction

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

Abstract

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Keywords

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