WzxWzy

WzxWzy refers to the Wzx/Wzy-dependent pathway for the biosynthesis of O antigen and related polysaccharides in Gram-negative bacteria. The term is commonly used to describe the coordinated action of two key enzymes, Wzx, a membrane-bound flippase, and Wzy, a polymerase, within the broader O-antigen biosynthesis system. In this pathway, the O-antigen repeating unit is assembled on a lipid carrier, undecaprenyl phosphate, on the cytoplasmic side of the inner membrane, and then transported across the membrane by Wzx to the periplasm, where Wzy links units into polymer chains. The chain length is modulated by a separate regulator, Wzz, and the finished O antigen is transferred to the lipid A-core during lipopolysaccharide assembly.

Genes encoding Wzx and Wzy are typically organized in dedicated operons or clusters dedicated to O-antigen biosynthesis. The pathway is widespread among Gram-negative bacteria, including members of the Enterobacteriaceae such as Escherichia coli and Salmonella, as well as other genera. WzxWzy-dependent mechanisms represent one of the major routes for O-antigen production, in contrast to the Wzm/Wzt ABC transporter-dependent pathway. Variation in Wzx and Wzy sequences, along with flanking regulatory elements, drives diversity in O-antigen structure and serotype specificity, influencing immune recognition and interactions with hosts.

Biological and medical significance arises from the role of O antigens in antigenic diversity, virulence, and immune evasion. Differences in O-antigen structure can affect serum resistance, colonization, and vaccine design. Because of its central role in serotype determination and pathogenicity, the WzxWzy-dependent pathway is a focus of microbiology and glycobiology research.

History and terminology: The components and their roles in O-antigen biosynthesis were characterized during the late 20th and early 21st centuries, with WzxWzy emerging as a concise way to refer to this specific biosynthetic route in bacterial polysaccharide research.