Metabolic model of central carbon and energy metabolisms of growing Arabidopsis thaliana in relation to sucrose translocation

Table 4 Comparison of metabolite turnover predicted by FBA with known values for Arabidopsis thaliana

Ratio of precursor turnover [mol i/mol j]	Compartment	This model					Published values	[Ref]
		Dark	Light
		Dark	FQR ^f) = 0 PR ^e) = 0.25	FQR / FNR ^f) = 0.37 PR ^e) = 0.25	FQR / FNR ^f) = 0.5 PR ^e) = 0.25	FQR / FNR ^f) = 0.1 PR ^e) = 0
Photon/CO₂	mesophyll	-	16.13	17.12	18.16	11.96	9.55	[27]
Photon/NO ⁻₃	mesophyll	-	104.37	110.71	117.46	77.38	75.87	[27]
CO₂/NO ⁻₃	mesophyll	-	6.47	6.47	6.47	6.48	7.95	[27]
P/O	mesophyll mitochondrion	4.62	4.99	4.98	4.58	4.99	2.5 – 5	[75]
T.ATP/ATP ^a)	plastid	1	+0.178 [import]	0	0	+0.083 [import]
NADP⁺-MDH/NADPH ^b)	plastid	0	−0.147 [export]	−0.063 [export]	0	−0.095 [export]
T.H⁺/H⁺ ^c)	plastid	0	−0.050 [export]	0	0	−0.002 [export]
ATP/NADPH	plastid	0.35	1.44	1.57	1.68	1.42	1.3 – 1.5	[63, 73]
ATP/NADH	mesophyll mitochondria	2.63	2.50	2.49	2.64	2.49	up to 3	[74]
H ⁺_in /ATP	plastid	-	4.0	4.0	4.0	4.0	4	[57, 58]
RQ ^d)	plant	1.83	-	-	-	-	0.8-1.6	[63]
Metabolite turnover [mol i/mol X]
ATP (× 10¹¹)	plastid	0.31	8.04	7.94	8.70	5.53
NADPH (× 10¹¹)	plastid	0.87	5.59	5.04	5.18	3.89
H⁺-turnover (× 10¹²)	plastid	0.17	2.75	3.15	3.45	2.05

The turnover are quantified for different light conditions (dark vs. light) and different involvement of cyclic electron flow through photosynthesis system assuming fixed degree of photorespiration (either 20 % of 0 % of photosynthesis)
FQR - ferredoxin-plastoquinone reductase, flux through FQR is the cyclic electron flow through the photosynthesis light reactions; FNR - ferredoxin-NADP⁺-oxidoreductase (EC 1.18.1.2), flux through FNR is the non-cyclic electron flow through the photosynthesis; NADP⁺-MDH – NADP⁺-dependent malate dehydrogenase (EC 1.1.1.82), part of malate/oxaloacetate shuttle, which translocate excess of reduced equivalent to mitochondria; photoresp. – photorespiration; X – biomass
^a) – part of ATP from the total ATP turnover in plastid, which is exchanged with cytoplasm through ATP/ADP translocator
^b)– part of NADPH from total NADPH turnover in plastid, which is exchanged with cytoplasm through malate/oxaloacetate shuttle
^c)– part of H⁺ from the total H⁺ turnover in plastid, which is exchanged with cytoplasm through transporter
^d)– respiratory quotient
^e)– photorespiration/photosynthesis ratio, constrain PR = 0.25 is the ratio between flux through photorespiration and photosynthesis, particularly through RuBisCo in Calvin-Benson cycle
^f)– FQR/FNR ratio represents ratio between cyclic and non-cyclic electron flows in photosynthesis light reactions

ISSN: 1471-2229