Involved in the biosynthesis of pyocyanine, a blue-pigmented phenazine derivative, which plays a role in virulence. Converts phenazine-1-carboxylate (PCA) to 5-methylphenazine-1-carboxylate (5-methyl-PCA). phenazine-1-carboxylate + S-adenosyl-L-methionine = 5-methyl-phenazine-1-carboxylate + S-adenosyl-L-homocysteine In vitro, requires PhzS for activity. Secondary metabolite biosynthesis; pyocyanine biosynthesis. Homodimer in solution (PubMed:16946471, PubMed:17253782). Probably interacts transiently with PhzS (PubMed:17253782). Contains an N-terminal dimerization domain. The C-terminal region contains the S-adenosyl-L-methionine binding site. Belongs to the class I-like SAM-binding methyltransferase superfamily. Cation-independent O-methyltransferase family.