TABLE 2.
Influence of calcium and iron concentrations on Pel activities using PGA and 45% esterified pectin as substrates
| Substrate | Cation concn (mM) | Enzyme activity (%) |
|||
|---|---|---|---|---|---|
| Pel-22 |
Pel-66 (Ca2+) | Pel-90 (Ca2+) | |||
| Ca2+ | Fe2+ | ||||
| PGA | 0 | 100 (9.86) | 100 (6.33) | 100 (16.18) | 100 (12.03) |
| 0.01 | 161.66 (8.33) | 163.79 (15.9) | 149.2 (7.19) | 155.47 (20.39) | |
| 0.02 | 168.33 (10.10) | 180.33 (5.18) | 143.45 (5.6) | 176.58 (0.82) | |
| 0.05 | 185 (14.50) | 193.62 (8.78) | 202.79 (7.32) | 210.33 (8.31) | |
| 0.1 | 213 (11) | 235.75 (6.34) | 231.38 (1.15) | 261.38 (13.61) | |
| 0.2 | 178.33 (13.16) | 185.63 (6.42) | 187.99 (2.53) | 193.5 (15.29) | |
| 0.5 | 141.66 (8.80) | 143.31 (12.26) | 138.42 (1.21) | 108.54 (12.11) | |
| 1 | 121.66 (4.80) | 121.36 (9.52) | 38.13 (1.5) | 32.98 (3.96) | |
| 45% esterified pectin | 0 | 100 (5.89) | 100 (12.56) | 100 (14.32) | 100 (8.12) |
| 0.01 | 149.76 (12.73) | 158.12 (7.32) | 142.36 (3.4) | 141.79 (2.94) | |
| 0.02 | 178.35 (15.39) | 185.7 (6.1) | 162.31 (3.8) | 178.64 (18.32) | |
| 0.05 | 213.54 (13.54) | 228.18 (8.18) | 211.58 (2.4) | 215.54 (1.91) | |
| 0.1 | 266.8 (9.02) | 279.67 (4.87) | 272.28 (7.99) | 251.42 (11.27) | |
| 0.2 | 271.01 (10.64) | 281.32 (4.12) | 344.71 (5.28) | 283.67 (1.93) | |
| 0.5 | 274.25 (15.74) | 272 (4.8) | 361.13 (7.88) | 304.59 (14.44) | |
| 1 | 274.34 (9.49) | 259.65 (1.25) | 375.84 (12.46) | 369.33 (14.79) | |
Activity under standard conditions (100 mM Tris-HCl, 1 g/liter PGA, and pH 7.5 or 8, or 100 mM Tris-HCl, 1 g/liter pectin [45% esterification], and pH 7.5 or 8) without any added cation was used as a reference (100%). The influence of the cation concentration was determined by using the corresponding chloride or sulfate salt from 0 to 1 mM. Each result reported is the average of three independent experiments, and the standard deviations (±) are indicated in parentheses.