Table 1. Enzyme kinetic inhibition constants.
| KM (μM) | Ki(mM) | α | β | Inhibition | ||
|---|---|---|---|---|---|---|
| AgIMPDH | 51±8 | GMP | 0.60±0.1 | − | − | Competitive |
| GDP | 0.21±0.04 | 6.5±0.8 | 0.033±0.005 | Mixed type | ||
| GTP | 0.16±0.04 | 4.1±0.7 | 0.24±0.05 | Mixed type | ||
| HsIMPDH1 | 41±2 | GMP | 0.96±0.08 | − | − | Competitive |
| GDP | 0.23±0.04 | 4.7±0.7 | 0.12±0.04 | Mixed type | ||
| GTP | 0.54±0.06 | 3.8±0.5 | 0.11±0.04 | Mixed type | ||
| HsIMPDH2 | 31±4 | GMP | 1.3±0.2 | − | − | Competitive |
| GDP | 0.61±0.06 | 6.6±0.8 | 0.14±0.05 | Mixed type | ||
| GTP | 0.48±0.06 | 3.0±0.4 | 0.51±0.08 | Mixed type | ||
| BsIMPDH | 120±20 | GMP | 0.42±0.07 | − | − | Competitive |
| GDP | 2.3±0.4 | 2.9±0.4 | 0.8±0.1 | Mixed type—weak | ||
| GTP | − | − | − | No | ||
| EcIMPDH | 80±10 | GMP | 1.1±0.1 | − | − | Competitive |
| GDP | − | − | − | No | ||
| GTP | 0.68±0.07 | − | − | Competitive |
GDP, guanosine-5′-diphosphate; GMP, guanosine-5′-monophosphate; GTP, guanosine-5′-triphosphate.
Values are given with s.e. The type of inhibition is shown in the column on the far right. The parameter α represents the substrate–inhibitor heterotropic cooperative interaction and β is the fractional activity of the ternary enzyme–substrate-inhibitor complex, as described in the Methods section.