O-antigen group O:28ac polymerase yielding a long O antigen chain length (25 repeat units)
25.0 udcpdpgalnac_b1_4_glc_b1_3_gal3_a1_4_rmn_a1_3_qui3nac_p ⇌ 24.0 udcpdp_p + OA28ac__L_p