Determining Sugar Sequence Fidelity

Abstract

Unlike their nucleic acid and protein siblings, carbohydrate biopolymers have no templates to guide their synthesis. The polymerase enzymes that stitch them together ensure that they end up with the desired sequence of sugars and linkages. But little is known about the faithfulness of carbohydrate polymerases. DNA polymerases have varying degrees of fidelity; however, researchers don’t know whether the same is true for carbohydrate polymerases. New work on one such polymerase, galacto­furanosyltransferase 2 (GlfT2), suggests that it is. The findings may point to a general strategy for determining what controls the fidelity of the enzymes responsible for building critical cellular carbohydrates. GlfT2 catalyzes the synthesis of galactan in the cell wall of Mycobacterium tuberculosis. The enzyme uses uridine diphosphate (UDP) galactofuranose as a donor substrate to add 30 to 35 galactofuranose residues with alternating β-(1→5) and β-(1→6) linkages to the growing galactan chain. Researchers are trying to fig...