Table 1. Determination of the glucan primer preference of AtSS1.
AtSS1 protein was treated with either 20 mM DTTred or 20 mM DTTox to promote protein reduction and oxidation, respectively. All acceptors were used in 10 mM concentration except for glycogen which was 1 mg mL-1. The activity was assayed by SCGA. Results are the mean of two independent experiments (±SD) and are expressed as turnovers of enzyme per minute.
| Acceptor type | Reduced AtSS1 | Oxidized AtSS1 | ||
|---|---|---|---|---|
| Enzyme activity Ared | Activity relative to maltotriose (%) | Enzyme activity Aox | Redox sensitivity (%)(Ared-Aox)/ Ared)x100 | |
| Glucose | 0.21±0.3 | <1 | 0.02±0.4 | 91 |
| Maltose | 24.0±0.7 | 20 | 4.4±0.1 | 82 |
| Maltotriose | 125.6±0.6 | 100 | 27.7±0.5 | 78 |
| Maltotetraose | 129.1±2.5 | 103 | 28.8±0.1 | 78 |
| Maltopentaose | 145.3±2.8 | 116 | 22.2±0.2 | 85 |
| Maltohexaose | 112.7±2.5 | 90 | 16.7±0.1 | 85 |
| Maltoheptaose | 100.0±8.2 | 80 | 13.1±0.4 | 87 |
| Maltooctaose | 99.3±1.9 | 79 | 13.5±0.1 | 86 |
| Glycogen | 235.2±19.7 | 187 | 9.8±0.2 | 96 |
| Glycogen* | 4,276* | 3,404* | 178* | 96* |
*normalized to the non-reducing end (NRE) molarity in MOS. MOS NRE molarity (equivalent to MOS molarity): 10−2 mol L-1; glycogen NRE molarity: 5.5x10-4 mol L-1; ADP-glucose molarity: 10−3 mol L-1; AtSS1 molarity: 7.6x10-8 mol L-1. Glycogen branching density was 9% and the total number of glucose residues is 5.5x104 [28].