Table 1. Effects of phosphatase and ATP on HMGR activity.
Tissue and recombinant protein samples with HMGR activity (5–10 μg of protein in each sample) were incubated for 30 min alone in HMGR buffer without KH2PO4 (control), with 1 unit of lambda protein phosphatase (Phosphatase), with 1×10−8 M ATP (ATP) or with 1×10−8 M ATP plus approx. 100 μg of rat liver whole homogenate (ATP+rat liver homogenate). For both treatments containing ATP, EDTA was removed from the HMGR buffer. HMGR activity [nmol·(mg of protein)−1·min−1, ±S.E.M., n=4 determinations] was measured after treatment. N.D., not determined.
| HMGR activity [nmol·(mg of protein)−1·min−1] | ||||
|---|---|---|---|---|
| HMGR source | Control | Phosphatase | ATP | ATP+rat liver homogenate |
| Purified rec-HMGR1 | 5520±140 | 5548±182 | 5508±104 | 5550±88 |
| Intact male MO supernatant | 66.5±14.1 | 66.4±12.8 | 67.2±14.8 | 64.8±10.2 |
| ESA male MO supernatant | 246.1±34.5 | 252.3±32.6 | 261.8±35.2 | 249.6±15.9 |
| Intact female MO supernatant | 25.4±4.1 | 24.8±4.5 | 24.5±1.9 | 26.8±2.4 |
| Purified Psm-HMGR | 3.6±0.1 | 3.7±0.1 | 3.6±0.2 | 3.5±0.2 |
| Rat liver whole homogenate | 5.6±0.3 | 9.3±0.2 | 0.1±0.0 | N.D. |