title: Transcription regulation is demonstrated for five key enzymes in Giardia intestinalis cyst wall polysaccharide biosynthesis.
abstract: The cyst wall of Giardia intestinalis contains proteins and a novel N-acetylgalactosamine (GalNAc) polysaccharide, which is its major constituent. GalNAc is not present in growing trophozoites, but is synthesized during encystment via an inducible pathway of enzymes that produce UDP-GalNAc from fructose 6-phosphate. This report focuses on the regulation of these enzymes and thus the genes for glucosamine 6-phosphate N-acetyltransferase (GNA), phosphoacetylglucosamine mutase (AGM), UDP-N-acetylglucosamine pyrophosphorylase (UAP), and UDP-N-acetylglucosamine 4-epimerase (UAE) were cloned and expressed in Escherichia coli. Each of these expressed enzymes had the predicted activity and was used to generate antibodies. Northern and Western blot analyses demonstrated that both the mRNA and protein levels for all of these enzymes increase during encystment. Nuclear run-on assays of these and the previously analyzed glucosamine 6-phosphate deaminase (GNP; glucosamine 6-P isomerase) showed that all of the genes responsible for UDP-GalNAc synthesis during encystment are induced at the transcription level.
authors.affiliation: Department of Biological, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA.
authors.forename: Alex B
authors.initials: AB
authors.lastname: Lopez
authors.forename: Keriman
authors.initials: K
authors.lastname: Sener
authors.forename: Edward L
authors.initials: EL
authors.lastname: Jarroll
authors.forename: Harry
authors.initials: H
authors.lastname: van Keulen
mesh_terms: D000116:Acetylgalactosamine / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D000123:Acetyltransferases / Q000235:genetics / Q000302:isolation & purification; D000818:Animals; D002238:Carbohydrate Epimerases / Q000235:genetics / Q000302:isolation & purification; D003001:Cloning, Molecular; D004798:Enzymes / Q000145:classification / Q000235:genetics; D005786:Gene Expression Regulation; D016829:Giardia lamblia / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development* / Q000502:physiology; D051081:Glucosamine 6-Phosphate N-Acetyltransferase; D006801:Humans; D008969:Molecular Sequence Data; D009713:Nucleotidyltransferases / Q000235:genetics / Q000302:isolation & purification; D017875:Phosphotransferases (Phosphomutases) / Q000235:genetics / Q000302:isolation & purification; D011134:Polysaccharides / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D014158:Transcription, Genetic
chemical_list: D004798:Enzymes; D011134:Polysaccharides; D012333:RNA, Messenger; D000123:Acetyltransferases; D051081:Glucosamine 6-Phosphate N-Acetyltransferase; D009713:Nucleotidyltransferases; C023226:UDPacetylglucosamine pyrophosphorylase; D002238:Carbohydrate Epimerases; C023223:UDP-N-acetylglucosamine 4-epimerase; D017875:Phosphotransferases (Phosphomutases); C018718:phosphoacetylglucosamine mutase; D000116:Acetylgalactosamine