Table 1. PP2C, but not PP1, PP2A, or PP2B, dephosphorylates phospho-Ser-845 of mGluR3.

	Dephosphorylation, % phosphate removed
	PP2Cβ	PP1	PP2B	PP2A
P-mGluR3 peptide	16	1	0	0
P-moesin peptide	20
P-T34 DARPP 32			25	18
Phosphorylase a		26

The activities of purified PP1, PP2A, PP2B, and PP2C were measured under initial-rate conditions by using a mGluR3 peptide (residues 830–859) phosphorylated at Ser-845 by PKA (100 μM), a phosphomoesin peptide (residues 554–560) (100 μM), ³²P-labeled Thr-34 DARPP-32 (1 μM), and ³²P-labeled phosphorylase a (10 μM) as described (see Materials and Methods). Relative rates of dephosphorylation are expressed as percentage of total phosphate released in the presence of phosphatase in 10 min at 30°C. Data represent means of two independent experiments, performed in duplicate.