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Molecule Parameter List for PLA2*-Ca

The statistics table lists the distribution of a molecule acting either as a substrate, product, enzyme or as a molecule within the network. The text color of a molecule is highlighted by color.

Statistics

PLA2*-Ca participated as	Molecule	Sum total of	Enzyme	Substrate of an enzyme	Product of an enzyme	Substrate in Reaction	Product in Reaction
No. of occurrences	1	0	1	0	0	0	1

Accession and Pathway Details

Accession Name	Accession No.	Accession Type	Pathway Link
MAPK-bistability -fig1c	35	Network	Shared_Object_MAPK-bistability-fig1c,  Sos,  PKC,   MAPK,  PLA2,  Ras,   PDGFR
Model for figure 1c in Bhalla US et al. Science (2002) 297(5583):1018-23. The demo for this figure is available here. This synaptic signaling model is without the MKP-1 feedback, so it is bistable and remains so over long periods.

PLA2*-Ca acting as a Molecule in  MAPK-bistability-fig1c Network

Name	Accession Name	Pathway Name	Initial Conc. (uM)	Volume (fL)	Buffered
PLA2*-Ca	MAPK-bistability -fig1c Accession No. : 35	PLA2 Pathway No. : 183	0	1000	No
Phosphorylated and active form of PLA2. Several kinases act on it: PKA: Wightman et al JBC 257 pp6650 1982 PKC: Many refs, eg Gronich et al JBC 263 pp 16645, 1988 but see Lin etal MAPK: Lin et al, Cell 72 pp 269, 1993. Show 3x with MAPK but not PKC alone The Nemenoff assays are conducted in rather high Ca so I have assumed a Ca binding step.

PLA2*-Ca acting as an Enzyme in  MAPK-bistability-fig1c Network

Enzyme Molecule / Enzyme Activity	Accession Name	Pathway Name	Km (uM)	kcat (s^-1)	Ratio	Enzyme Type	Reagents
PLA2*-Ca / kenz	MAPK-bistability -fig1c Accession No. : 35	PLA2 Pathway No. : 183	20	120	4	explicit E-S complex	Substrate APC Product AA
This form should be 3 to 6 times as fast as the Ca-only form, from Lin et al 1993 Cell 269-278 Nemenoff et al 1993 JBC 268:1960 Several forms contribute to the Ca-stimulated form, so this rate has to be a factor larger than their total contribution. I assign Vmax as the scale factor here because there is lots of APC substrate, so all the PLA2 complex enzymes are limited primarily by Vmax.

PLA2*-Ca acting as a Product in a reaction in  MAPK-bistability-fig1c Network

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 reaction are not consider.

Name	Accession Name	Pathway Name	Kf	Kb	Kd	tau	Reagents
PLA2*-Ca-act	MAPK-bistability -fig1c Accession No. : 35	PLA2 Pathway No. : 183	6 (uM^-1 s^-1)	0.1 (s^-1)	Kd(bf) = 0.0167(uM)	-	Substrate Ca PLA2* Product PLA2*-Ca
Nemenoff et al 1993 JBC 268:1960 report a 2X to 4x activation of PLA2 by MAPK, which seems dependent on Ca as well. This reaction represents this activation. Rates are scaled to give appropriate fold activation.