Table 2.

Estimated in Vivo Mass-Action Ratios of Enzyme and Transport Reactions Involved in Suc-to-Starch Conversion

		Molar Mass-action Ratio
Reaction	Formula	Attached Tubers	Detached Tubers	Theoretical Equilibrium Constant (Keq)
SuSy (cytosol)		0.181	0.632	0.15 to 0.56a
UGPase (cytosol)		1.48	3.21	3.2b
Fructokinase (cytosol)		0.032	0.085	851c
Phosphoglucoisomerase (cytosol)		3.47	4.05	2c
PGM (cytosol)		11.9	10.5	19c
Glc-6-P/Pi translocator		2.04	2.97	1d
3PGA/Pi translocator		1.85	3.31	1d
Adenylate translocator		0.359	0.961	1d
PGM (plastid)		0.046	0.078	0.053c
AGPase (plastid)		1.6 × 10−2	4 × 10−4	1e
Inorganic pyrophosphatase (plastid)		0.323	0.373	1000b

The data from Table 1 were used to calculate the in vivo molar mass-action ratios (ratio of product to substrate concentration) for each reaction. The theoretical equilibrium constant (ratio of product/substrate concentration) at which the net flux is zero) of each reaction is shown for comparison.

^aGeigenberger et al. (1993).

^bWeiner et al. (1987).

^cStryer (1990).

^dEstimated value.

^eKruger (1997).