Figure 1.

Substrate specificities of Acanthamoeba MIHCK, 35K, and PAK1. Kinase activities were determined as described with the synthetic peptides described in Table 1 as substrates. MIHCK was fully activated by autophosphorylation (11) before its assay; expressed 35K is fully active without autophosphorylation (17). His-PAK1 is constitutively active (U.G.K., unpublished observations). To compare their relative substrate specificities, the activities were normalized to their activities with PC9 as substrate as 100; the actual specific activities with PC9 were: MIHCK, 26 μmol·min⁻¹·mg⁻¹; 35K, 27 μmol·min⁻¹·mg⁻¹; and His-PAK1, 0.37 μmol·min⁻¹·mg⁻¹.