<?xml version="1.0" encoding="UTF-8" ?>
<sbml xmlns="http://www.sbml.org/sbml/level3/version1/core" level="3" version="1">
  <model substanceUnits="mole" volumeUnits="litre" timeUnits="second" extentUnits="mole">
    <listOfUnitDefinitions>
	    <unitDefinition id="per_second">
	      <listOfUnits>
	        <unit kind="second" exponent="-1" scale="0" multiplier="1"/>
	      </listOfUnits>
	    </unitDefinition>
	    <unitDefinition id="mole_per_litre">
	      <listOfUnits>
	        <unit kind="mole"  exponent="1"  scale="0" multiplier="1"/>
	        <unit kind="litre" exponent="-1" scale="0" multiplier="1"/>
	      </listOfUnits>
	    </unitDefinition>
	    <unitDefinition id="litre_per_mole_per_second">
	      <listOfUnits>
	        <unit kind="litre"  exponent="1"  scale="0" multiplier="1"/>
	        <unit kind="mole"   exponent="-1" scale="0" multiplier="1"/>
	        <unit kind="second" exponent="-1" scale="0" multiplier="1"/>
	      </listOfUnits>
	    </unitDefinition>
    </listOfUnitDefinitions>
    <listOfCompartments>
      <compartment id="cell" size="1" spatialDimensions="3" constant="true"/>
    </listOfCompartments>
    <listOfSpecies>
      <species id="E" compartment="cell" initialConcentration="0.5" constant="false"
               hasOnlySubstanceUnits="false" boundaryCondition="true"/>
      <species id="S"  compartment="cell" initialConcentration="1.0" constant="false"
               hasOnlySubstanceUnits="false" boundaryCondition="false"/>
      <species id="ES" compartment="cell" initialConcentration="0.5" constant="false"
               hasOnlySubstanceUnits="false" boundaryCondition="true"/>
      <species id="P" compartment="cell" initialConcentration="0" constant="false"
               hasOnlySubstanceUnits="false" boundaryCondition="false"/>
      <species id="E_total" compartment="cell" initialConcentration="1.0" constant="true"
               hasOnlySubstanceUnits="false" boundaryCondition="true"/>
    </listOfSpecies>
    <listOfParameters>
      <parameter id="k1_on"  value="1"   units="litre_per_mole_per_second" constant="true"/>
      <parameter id="k1_off" value="0.5" units="per_second" constant="true"/>
      <parameter id="k2"     value="0.5" units="per_second" constant="true"/>
    </listOfParameters>
    <listOfRules>
      <algebraicRule>
        <math xmlns="http://www.w3.org/1998/Math/MathML">
          <apply>
          <minus/>
            <apply> 
              <times/> <ci> k1_on </ci> <ci> E </ci> <ci> S </ci> 
            </apply>
            <apply>
              <times/>
              <apply> <plus/> <ci> k1_off </ci> <ci> k2 </ci> </apply>
              <ci> ES </ci>
            </apply>
          </apply>
        </math>
      </algebraicRule>
      <algebraicRule>
        <math xmlns="http://www.w3.org/1998/Math/MathML">
          <apply>
          <minus/>
            <apply> <plus/> <ci> E </ci> <ci> ES </ci> </apply>
            <ci> E_total </ci>
          </apply>
        </math>
      </algebraicRule>
    </listOfRules>
    <listOfReactions>
      <reaction id="r1" reversible="true" fast="false">
        <listOfReactants>
          <speciesReference species="E" stoichiometry="1" constant="true"/>
          <speciesReference species="S" stoichiometry="1" constant="true"/>
        </listOfReactants>
        <listOfProducts>
          <speciesReference species="ES" stoichiometry="1" constant="true"/>
        </listOfProducts>
        <kineticLaw>
          <math xmlns="http://www.w3.org/1998/Math/MathML">
            <apply>
            <times/>
              <ci> cell </ci>
              <apply>
              <minus/>
                <apply> <times/> <ci> k1_on </ci> <ci> E </ci> <ci> S </ci> </apply>
                <apply> <times/> <ci> k1_off </ci> <ci> ES </ci> </apply>
              </apply>
            </apply>
          </math>
        </kineticLaw>
      </reaction>
      <reaction id="r2" reversible="false" fast="false">
        <listOfReactants>
          <speciesReference species="ES" stoichiometry="1" constant="true"/>
        </listOfReactants>
        <listOfProducts>
          <speciesReference species="E" stoichiometry="1" constant="true"/>
          <speciesReference species="P" stoichiometry="1" constant="true"/>
        </listOfProducts>
        <kineticLaw>
          <math xmlns="http://www.w3.org/1998/Math/MathML">
            <apply> <times/> <ci> cell </ci> <ci> k2 </ci> <ci> ES </ci> </apply>
          </math>
        </kineticLaw>
      </reaction>
    </listOfReactions>
  </model>
</sbml>
