Object Type:	enz

Description:	Enzyme activity for a pre-existing pool. An enz does two
		things: it handles the reactions in the Michaelis-Menten (MM)
		scheme below, and it also acts as a pool to represent the
		enzyme-substrate complex. It can only be
		created on a pool, it is not an independent object.

		The MM scheme is modeled as:
					k1		k3
 		Substrate + Enzyme  <-----> EnzComplex ----> Enz + Prd
   				    	k2

		The enz is really a utility object, as it replaces
		two reacs and a pool, but does not add anything extra.
		
Author:		U. S. Bhalla, National Centre for Biological Sciences,
		Bangalore, India. (1993).

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ELEMENT PARAMETERS

DataStructure:	enz_type  [in src/kinetics/kin_struct.h]

Size:		bytes

Fields:		CoComplex		Concentration of enz-substrate complex.
					CoComplex = nComplex/vol
		CoComplexInit		Initial concentration of enz-substrate
					complex.
					CoComplex gets set to this value on
					RESET.
                nComplex		Number of molecules of complex.
		nComplexInit		Initial number of molecules of complex.
					'nComplex'gets set to this value on
					RESET.
		vol			Volume occupied by enzyme. Often
					involves scale factor so as to have
					direct conversion from 'n' to some
					sensible units of Co, such as
					micromolar.
		sA			A state variable to pass to substrate
					in messages.
		pA			A state variable to pass to products
					in messages.
		eA			A state variable to pass to parent
					enzyme pool in messages.
		B			B state variable to pass to substrate
					and parent enzyme pool in messages
		k1,k2,k3		Michaelis-Menten parameters. 


		keepconc		Flag determining whether to change
					concs or n when volume changes
		usecomplex		Flag. Determines whether the enzyme
					complex is used when the parent enzyme
					is involved in other reactions.
					Consider:

					E + A <----> E.A
					
					where E is a pool reacting with A.
					Suppose E has an enzyme site. Then,
					whenever some of the enzyme is complexed
					with a substrate, the conc of E
					decreases unless 'usecomplex' is true.
		ksum			Internal variable. ksum = k2 + k3.
		

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SIMULATION PARAMETERS

Function:	EnzFunc  [in src/kinetics/enz.c]

Classes:	segment

Actions:	PROCESS
		RESET
		SET

Messages: 	ENZYME		n	[n is number of molecules of enzyme
					pool to which this site is attached]
                SUBSTRATE  	n     	[Number of molecules of substrate]
                VOL		vol	[volume of enzyme pool]
                INTRAMOL	n	[Total number of molecules in an
					intramolecular reaction]


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Notes: See pool documentation for example of use.

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