Effects of human liver cytosol and other proteins on DPH oxidation activities catalyzed by human liver microsomes
| Microsomes | Cytosol (conditions) | 4′-HPPH | 3′-HPPH | 3′,4′-diHPPH |
|---|---|---|---|---|
| pmol product/min/mg microsomal protein | ||||
| Experiment 1 | ||||
| HL-4 | 9.8 | <0.1 | 0.2 | |
| HL-4 | HL-1 | 11.5 | <0.1 | 5.6 |
| HL-4 | HL-4 | 10.0 | <0.1 | 1.1 |
| HL-4 | HL-5 | 10.4 | <0.1 | 3.1 |
| HL-4 | HL-10 | 12.6 | 3.2 | 1.1 |
| HL-10 | 14.0 | 0.7 | 0.6 | |
| HL-10 | HL-1 | 14.7 | <0.1 | 4.8 |
| HL-10 | HL-4 | 14.3 | 0.7 | 1.2 |
| HL-10 | HL-5 | 14.1 | <0.1 | 2.4 |
| HL-10 | HL-10 | 15.4 | 4.3 | 1.1 |
| Experiment 2 | ||||
| HL-4 | HL-4 | 10.3 | <0.1 | 1.1 |
| HL-4 | HL-4 (40°C, 15 min) | 9.4 | <0.1 | 1.1 |
| HL-4 | HL-4 (50°C, 15 min) | 7.9 | <0.1 | 1.0 |
| HL-4 | HL-10 | 13.1 | 3.1 | 1.1 |
| HL-4 | HL-10 (40°C, 15 min) | 12.1 | 2.6 | 1.0 |
| HL-4 | HL-10 (50°C, 15 min) | 10.6 | 2.5 | 1.0 |
| HL-4 | BSA | 14.9 | <0.1 | 0.2 |
| HL-4 | Rabbit serum | 14.0 | <0.1 | 0.2 |
DPH (100 μM) was incubated at 37°C for 30 min with human liver microsomes (HL-4 or HL-10, 1.0 mg protein/ml) in the absence or presence of liver cytosol or preheated cytosol in different conditions, BSA, or rabbit serum (5.0 mg protein/ml). Product formation activities catalyzed by each cytosol alone were not observed (<0.1 pmol/min/mg protein). Results are presented as means of duplicate determinations.