TABLE 2.
Effects of simulated enzymopathies in glycolytic enzymes on steady-state flux space
| Glycolytic enzymes |  |
Constraining? | Systemic 
|
Systemic 
|
Restricted 
|
Percentage of steady-state flux space remaining | Hemolytic anemia?* |
|---|---|---|---|---|---|---|---|
| Hexokinase (HK) | 1.5 | Yes | 1.50 | 0.48 | 0.74 | 0.02% | Yes |
| Phosphofructokinase (PFK) | 250 | No | 1.58 | 0.31 | 0.63 | 0.21% | Variable |
| Triose phosphate isomerase (TPI) | 1000 | No | 1.58 | 0.31 | 0.63 | 0.21% | Yes |
| Aldolase (ALD) | 1000 | No | 1.58 | 0.31 | 0.63 | 0.21% | Yes |
| Lactate dehydrogenase (LDH) | 1000 | No | 2.81 | 0.09 | 0.77 | 0.56% | No |
| Pyruvate kinase (PK) | 250 | No | 3.21 | 1.17 | 1.68 | 0.83% | Yes |
| Enolase (EN) | 1000 | No | 3.21 | 1.17 | 1.68 | 0.84% | Yes |
| Phosphoglucoisomerase (PGI) | 1000 | No | 1.48 | −0.77 | −0.21 | 1.0% | Yes |
| Phosphoglycerate kinase (PGK) | 1000 | No | 2.91 | 0.87 | 1.38 | 2.2% | Usually |
| Diphosphoglycerate phosphatase (DPGase) | 0.52 | Yes | 0.52 | 0.3 | 0.36 | 29% | No |
| Diphosphoglyceromutase (DPGM) | 12 | No | 1.43 | 0.3 | 0.58 | 47% | No |
Several conditions have been identified that decrease the effectiveness of enzymes in the red blood cells. The effect of a reduction in the possible steady-state ranges of fluxes on the steady-state flux space as a whole was simulated by decreasing the maximum allowable reaction flux through the reaction catalyzed by the given enzyme. The columns of the table show: 1), the enzyme defect being simulated; 2), the corresponding 
; 3), whether the 
is constraining on the system; 4), the actual maximum flux rate for the reaction in the network; 5), the actual minimum flux rate (
) for the reaction in the network; 6), to what extent 
is restricted to constrain the allowable flux range for the reaction to one-quarter of its original value; 7), the percentage drop in the volume of the steady-state flux space corresponding to the simulated enzymopathy; and 8), whether defects in an enzyme had been experimentally determined to cause anemia or not.
Taken from Tanaka et al. (1990).