Processing O-glycan core 1, Gal beta 1-3GalNAc alpha-R. Specificities of core 2, UDP-GlcNAc: Gal beta 1-3 GalNAc-R(GlcNAc to GalNAc) beta 6-N-acetylglucosaminyltransferase and CMP-sialic acid: Gal beta 1-3GalNAc-R alpha 3-sialyltransferase.
To elucidate control mechanisms of O-glycan biosynthesis in leukemia and to develop biosynthetic inhibitors we have characterized core 2 UDP-GlcNAc:Gal beta 1-3GalNAc-R(GlcNAc to GalNAc) beta 6-N-acetylglucosaminyltransferase (EC 2.4.1.102; core 2 beta 6-GlcNAc-T) and CMP-sialic acid: Gal beta 1-3GalNAc-R alpha 3-sialyltransferase (EC 2.4.99.4; alpha 3-SA-T), two enzymes that are significantly increased in patients with chronic myelogenous leukemia (CML) and acute myeloid leukemia (AML). We observed distinct tissue-specific kinetic differences for the core 2 beta 6-GlcNAc-T activity; core 2 beta 6-GlcNAc-T from mucin secreting tissue (named core 2 beta 6-GlcNAc-T M) is accompanied by activities that synthesize core 4 [GlcNAc beta 1-6(GlcNAc beta 1-3)GalNAc-R] and blood group I [GlcNAc beta 1-6(GlcNAc beta 1-3)Gal beta-R] branches; core 2 beta 6-GlcNAc-T in leukemic cells (named core 2 beta-GlcNAc-T L) is not accompanied by these two activities and has a more restricted specificity. Core 2 beta 6-GlcNAc-T M and L both have an absolute requirement for the 4- and 6-hydroxyls of N-acetylgalactosamine and the 6-hydroxyl of galactose of the Gal beta 1-3GalNAc alpha-benzyl substrate but the recognition of other substituents of the sugar rings varies, depending on the tissue. alpha 3-sialyltransferase from human placenta and from AML cells also showed distinct specificity differences, although the enzymes from both tissues have an absolute requirement for the 3-hydroxyl of the galactose residue of Gal beta 1-3GalNAc alpha-Bn. Gal beta 1-3(6-deoxy)GalNAc alpha-Bn and 3-deoxy-Gal beta 1-3GalNAc alpha-Bn competitively inhibited core 2 beta 6-GlcNAc-T and alpha 3-sialyltransferase activities, respectively.
Kuhns
W
W
Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada.
Rutz
V
V
Paulsen
H
H
Matta
K L
KL
Baker
M A
MA
Barner
M
M
Granovsky
M
M
Brockhausen
I
I
D000818:Animals; D002240:Carbohydrate Sequence; D002413:Cations, Divalent / Q000494:pharmacology; D002645:Chickens; D006801:Humans; D007700:Kinetics; D007938:Leukemia / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D015394:Molecular Structure; D017351:N-Acetylglucosaminyltransferases / Q000037:antagonists & inhibitors / Q000737:chemistry*; D009928:Organ Specificity / Q000502:physiology; D011134:Polysaccharides / Q000096:biosynthesis / Q000737:chemistry*; D051381:Rats; D012799:Sialyltransferases / Q000037:antagonists & inhibitors / Q000737:chemistry*; D013379:Substrate Specificity; D013552:Swine; D014407:Tumor Cells, Cultured
D002413:Cations, Divalent; D011134:Polysaccharides; D017351:N-Acetylglucosaminyltransferases; D012799:Sialyltransferases