TABLE 3.
Substrate specificities and kinetic characteristics of mammalian cGMP-hydrolyzing PDEs
Values compiled from Bender and Beavo (2006a). The range of values is likely to be due to the different assay conditions and preparations of the respective enzymes in various laboratories.
| Isoenzyme | Substrate Preference |
Km |
Vmax |
||
|---|---|---|---|---|---|
| cGMP | cAMP | cGMP | cAMP | ||
| μM | μmol/min/mg | ||||
| PDE1A | cGMP > cAMP | 3–4 | 73–120 | 50–300 | 70–750 |
| PDE1B | cGMP > cAMP | 1–6 | 10–24 | 30 | 10 |
| PDE1C | cGMP = cAMP | 1–2 | 0.3–1 | N.D. | N.D. |
| PDE2A | cGMP = cAMP | 10 | 30 | 123 | 120 |
| PDE3A | cGMP < cAMP | 0.02–0.2 | 0.2 | 0.3 | 3–6 |
| PDE3B | cGMP < cAMP | 0.3 | 0.4 | 2 | 9 |
| PDE5A | cGMP ≫ cAMP | 1–6 | 90 | 1–3 | 1–3 |
| PDE6A/B | cGMP ≫ cAMP | 15 | 700 | 2300 | N.D. |
| PDE6C | cGMP ≫ cAMP | 17 | 610 | 1400 | N.D. |
| PDE9A | cGMP ≫ cAMP | 0.2–0.7 | 230 | N.D. | N.D. |
| PDE10A | cGMP < cAMP | 13 | 0.2–1 | N.D. | N.D. |
| PDE11A | cGMP = cAMP | 0.4–2 | 0.5–3 | N.D. | N.D. |
N.D., no reliable data currently available.