Catalyzes the pyruvylation of subterminal glucose in the exopolysaccharide (EPS) repeating unit. [4)-beta-D-GlcA-(1->4)-2-O-Ac-beta-D-GlcA-(1->4)-beta-D-Glc-(1->4)-[3-O-(CH3CH(OH)CH2C(O))-(R)-4,6-CH3(COO(-))C-beta-D-Gal-(1->3)-beta-D-Glc-(1->4)-beta-D-Glc-(1->4)-beta-D-Glc-(1->6)]-2-O-Ac-alpha-DGlc-(1->](n) + n phosphoenolpyruvate = [4)-beta-D-GlcA-(1->4)-2-O-Ac-beta-D-GlcA-(1->4)-beta-D-Glc-(1->4)-[3-O-(CH3CH(OH)CH2C(O))-(R)-4,6-CH3(COO(-))C-beta-D-Gal-(1->3)-(S)-4,6-CH3(COO(-))C-beta-D-Glc-(1->4)-beta-D-Glc-(1->4)-beta-D-Glc-(1->6)]-2-O-Ac-alpha-DGlc-(1->](n) + n phosphate Exopolysaccharide biosynthesis. Mutants form aberrant non-nitrogen-fixing nodules on peas. Belongs to the polysaccharide pyruvyl transferase family.