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Molecule Parameter List for PPhosphatase2A

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

*PPhosphatase2A* 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	4	0	0	0	0

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.

PPhosphatase2A acting as a Molecule in MAPK-bistability-fig1c Network

Name	Accession Name	Pathway Name	Initial Conc. (uM)	Volume (fL)	Buffered
PPhosphatase2A	MAPK-bistability -fig1c Accession No. : 35	Shared_Object_ MAPK-bistability -fig1c Pathway No. : 179	0.224	1000	No
Refs: Pato et al Biochem J 293:35-41(93); CoInit values span a range depending on source. Pato et al 1993 Biochem J 293:35-41 and Cohen et al 1988 Meth Enz 159:390-408 estimate 80 nM from muscle Zolneierowicz et al 1994 Biochem 33:11858-11867 report levels of 0.4 uM again from muscle, but expression is also strong in brain. Our estimate of 0.224 is between these two. There are many substrates for PP2A in this model, so I put the enzyme rate calculations here: Takai&Mieskes Biochem J 275:233-239 have mol wt 36 KDa. They report Vmax of 119 umol/min/mg i.e. 125/sec for k3 for pNPP substrate, Km of 16 mM. This is obviously unreasonable for protein substrates. For chicken gizzard myosin light chan, we have Vmax = 13 umol/min/mg or about k3 = 14/sec. Pato et al 1993 Biochem J 293:35-41 report caldesmon: Km = 2.2 uM, Vmax = 0.24 umol/min/mg. They do not think caldesmon is a good substrate. Calponin: Km = 14.3, Vmax = 5. Our values approximate these.

PPhosphatase2A 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
1	PPhosphatase2A / craf-deph	MAPK-bistability -fig1c Accession No. : 35	Shared_Object_ MAPK-bistability -fig1c Pathway No. : 179	15.6566	6	4.16667	explicit E-S complex	Substrate craf-1* Product craf-1
	See parent PPhosphatase2A for parms
2	PPhosphatase2A / MAPKK-deph	MAPK-bistability -fig1c Accession No. : 35	Shared_Object_ MAPK-bistability -fig1c Pathway No. : 179	15.6566	6	4.16667	explicit E-S complex	Substrate MAPKK* Product MAPKK-ser
	See: Kyriakis et al Nature 358 pp 417-421 1992 Ahn et al Curr Op Cell Biol 4:992-999 1992 for this pathway. See parent PPhosphatase2A for parms.
3	PPhosphatase2A / MAPKK-deph-ser	MAPK-bistability -fig1c Accession No. : 35	Shared_Object_ MAPK-bistability -fig1c Pathway No. : 179	15.6566	6	4.16667	explicit E-S complex	Substrate MAPKK-ser Product MAPKK
	See parent PPhostphatase2A description for rate details
4	PPhosphatase2A / craf**-deph	MAPK-bistability -fig1c Accession No. : 35	Shared_Object_ MAPK-bistability -fig1c Pathway No. : 179	15.6566	6	4.16667	explicit E-S complex	Substrate craf-1 Product** craf-1*
	Ueki et al JBC 269(22) pp 15756-15761 1994 show hyperphosphorylation of craf, so this is there to dephosphorylate it. Identity of phosphatase is assumed to be PP2A.

Database compilation and code copyright (C) 2022, Upinder S. Bhalla and NCBS/TIFR
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