Table 2.
Effect of buffer composition on kinetics of wild-type aldose reductase with dl-glyceraldehyde as substrate (n = 3)
| Buffer | Urea (1.0 M) | TMAO (0.5 M) | Vmax,* % of control | Km,* % of control |
|---|---|---|---|---|
| 0.01 M KPO4, pH 6.0 | − | − | 100.0 | 100.0a |
| + | − | 26.3 ± 0.2 | 23.7 ± 1.5 | |
| − | + | 54.4 ± 0.3 | 29.2 ± 1.0 | |
| + | + | 19.8 ± 0.3 | 9.5 ± 0.3 | |
| 0.01 M KPO4, pH 7.0 | − | − | 100.0 | 100.0b |
| + | − | 43.6 ± 0.6 | 45.5 ± 1.7 | |
| − | + | 76.3 ± 0.8 | 58.1 ± 1.2 | |
| + | + | 36.7 ± 0.2 | 26.4 ± 0.1 | |
| 0.10 M NaPO4, pH 7.0 | − | − | 100.0 | 100.0c |
| + | − | 46.0 ± 1.7 | 52.7 ± 2.8 | |
| − | + | 91.6 ± 0.6 | 81.7 ± 5.7 | |
| + | + | 39.1 ± 0.5 | 40.4 ± 0.9 |
*
All experimental values are significantly less (P < 0.05) than the controls, which contained no urea or TMAO. Control values (no urea or TMAO) for Km are a, 0.371 mM; b, 0.087 mM; and c, 0.141 mM.