Probing the mechanism of a fungal glycosyltransferase essential for cell wall biosynthesis. UDP-chitobiose is not a substrate for chitin synthase.
Chitin synthase is responsible for the biosynthesis of chitin, an essential component of the fungal cell wall. There is a long-standing question as to whether "processive" transferases such as chitin synthase operate in the same manner as non-processive transferases. The question arises from analysis of the polysaccharide structure--in chitin, for instance, each sugar residue is rotated approximately 180 degrees relative to the preceding sugar in the chain. This requires that the enzyme account for the alternating "up/down" configuration during biosynthesis. An enzyme with a single active site, analogous to the non-processive transferases--would have to accommodate a distorted glycosidic linkage at every other synthetic step. An alternative proposal is that the enzyme might assemble the disaccharide donor, addressing the "up/down" conformational problem prior to polymer synthesis. We present compelling evidence that this latter hypothesis is incorrect.
Chang
Robert
R
Department of Chemistry and Biochemistry-0358 University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0358, USA.
Yeager
Adam R
AR
Finney
Nathaniel S
NS
D002473:Cell Wall / Q000737:chemistry*; D002686:Chitin / Q000096:biosynthesis; D002687:Chitin Synthase / Q000502:physiology*; D004187:Disaccharides / Q000737:chemistry*; D016695:Glycosyltransferases / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D014530:Uridine Diphosphate / Q000737:chemistry*
D004187:Disaccharides; D002686:Chitin; C032438:chitobiose; D014530:Uridine Diphosphate; D016695:Glycosyltransferases; D002687:Chitin Synthase