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Reaction List for pathway CaRegulation (Pathway Number 110)

Kd is calculated only for second order reactions, like nA+nB <->nC or nA<->nC+nD, where n is number and A,B,C,D are molecules, where as for first order reactions Keq is calculated. Kd for higher order reactions is not considered.

	Name	Kf	Kb	Kd	tau	Substrate	Product
1	Ca-bind-to-Trans p	3600 (uM^-2 s^-1)	144 (s^-1)	Kd(af) = 0.2(uM)	-	Ca Ca CaTransp	CaTransp-2Ca
	Rates from Lauffenburger abd Linderman 1993 Receptors pg 200. Kd = KCa2 = 0.2 uM
2	Ca10-bind-Cal	0.0005 (uM^-5 s^-1)	1 (s^-1)	-	-	Ca5-Cal Ca-sequester Ca-sequester Ca-sequester Ca-sequester Ca-sequester	Ca10-Cal
	There are actually 5 Ca-sequester substrates for this reaction, along with Ca5-Cal. Due to system limitations only four are entered.
3	Ca15-bind-Cal	0.0005 (uM^-5 s^-1)	1 (s^-1)	-	-	Ca10-Cal Ca-sequester Ca-sequester Ca-sequester Ca-sequester Ca-sequester	Ca15-Cal
	There are actually 5 Ca-sequester substrates for this reaction, along with Ca10-Cal. Due to system limitations only four are entered.
4	Ca20-bind-Cal	0.0005 (uM^-5 s^-1)	1 (s^-1)	-	-	Ca15-Cal Ca-sequester Ca-sequester Ca-sequester Ca-sequester Ca-sequester	Ca20-Cal
	There are actually 5 Ca-sequester substrates for this reaction, along with Ca15-Cal. Due to system limitations only four are entered.
5	Ca25-bind-Cal	0.0005 (uM^-5 s^-1)	1 (s^-1)	-	-	Ca-sequester Ca-sequester Ca-sequester Ca-sequester Ca-sequester Ca20-Cal	Ca25-Cal
	There are actually 5 Ca-sequester substrates for this reaction, along with Ca20-Cal. Due to system limitations only four are entered.
6	Ca30-bind-Cal	0.0005 (uM^-5 s^-1)	1 (s^-1)	-	-	Ca25-Cal Ca-sequester Ca-sequester Ca-sequester Ca-sequester Ca-sequester	Ca30-Cal
	There are actually 5 Ca-sequester substrates for this reaction, along with Ca25-Cal. Due to system limitations only four are entered.
7	Ca35-bind-Cal	0.0005 (uM^-5 s^-1)	1 (s^-1)	-	-	Ca-sequester Ca-sequester Ca-sequester Ca-sequester Ca-sequester Ca30-Cal	Ca35-Cal
	There are actually 5 Ca-sequester substrates for this reaction, along with Ca30-Cal. Due to system limitations only four are entered.
8	Ca40-bind-Cal	0.0005 (uM^-5 s^-1)	1 (s^-1)	-	-	Ca-sequester Ca-sequester Ca-sequester Ca-sequester Ca-sequester Ca35-Cal	Ca40-Cal
	There are actually 5 Ca-sequester substrates for this reaction, along with Ca35-Cal. Due to system limitations only four are entered.
9	Ca5-bind-Cal	0.0005 (uM^-5 s^-1)	1 (s^-1)	-	-	Calseq Ca-sequester Ca-sequester Ca-sequester Ca-sequester Ca-sequester	Ca5-Cal
	There are actually 5 Ca-sequester substrates for this reaction, along with one Calseq. Due to system limitations only four are entered.
10	CaTraspATPase	25 (s^-1)	0 (#^-2 s^-1)	Not applicable**	-	CaTransp-2Ca	CaTransp Ca-sequester Ca-sequester
	kCa3 = 2 * Ca transporter rate since each step has 2 Ca++. = 0.5 uM/sec from Lauffenburger and Linderman 1993 Receptors pg200 The amount of the activated transporter is about 0.01 uM = 6e3#. from runs. So 0.01uM * kf * 2 = 0.5 uM/sec (no back reaction) so kf = 25, kb = 0 Alternatively, 6e3 * kf = 0.25 * 6e5, giving the same kf
11	inactivate_cap_ Ca	0 (#^-2 s^-1)	1 (s^-1)	Not applicable**	-	Ca-sequester Ca-sequester capacitive_Ca_ entry*	inact_cap_entry
	The Kd is set at about 3 uM so that at resting Ca the capacitative Ca entry is almost blocked. A 2nd order response makes the response steep.
12	IP3Rbind	0.05 (uM^-3 s^-1)	1 (s^-1)	Kd(af) = 2.7144(uM)	-	IP3R IP3 IP3 IP3	IP3R*
	Based on Lauffenburger and Linderman 1993 Receptors pg 200. The binding of IP3 on this reaction had a Hill coeff of 3. The eqns of Mahama and Linderman (cited in the book as 1993 a) are equivalent to the binding all occurring in a single step, so that is how I do it in this version. Their Ki1 is 0.07 uM. Lots of other data sources: Ramos-Franco et al, Biophys J 75, 1998: 834-39 have Ca sensitivity curves. At 250 nM free Ca, the EC50 for type1 is 58 nM and type 2 is 194 nM. Type 3 would be about 2 uM according to Newton et al, JBC 268(46), 1994: 28613-19. For the purposes of this model we use a Kd of 2.7 uM which is high but maybe OK at low calcium. The details of Ca interaction with the IP3R are not included in this model.

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Enzyme List

Reaction List