title: Are there two forms of beta 2-N-acetylglucosaminyltransferase I in rat testicular and epididymal fluids?
abstract: The activity of alpha 3-D-mannoside-beta-1,2-N-acetylglucosaminyltransferase I (GnT I; EC 2.4.1.101), which catalyzes the first step in the conversion of oligomannose to complex or hybrid N-glycans of glycoproteins, was detected in rat testicular and cauda epididymal fluids. The GnT I activity of testicular fluid had a pH optimum of 6.0, whereas that of the cauda epididymal fluid was optimal at pH 7.0. The enzyme in testicular fluid had an absolute requirement for either Co2+, or Mn2+, Mg2+ and Ca2+, the activity being stimulated by these cations in the above order, whereas that of cauda epididymal fluid had an absolute requirement for Mn2+ or Ca2+, with Co2+ and Mg2+ being ineffective. The specific activity of GnT I in cauda epididymal fluid was somewhat higher than in testicular fluid. The apparent Km value for alpha 1-3 alpha 1-6mannopentaose of GnT I in the testicular and epididymal fluids was 0.57 and 0.38 mM, respectively. The substrate specificity for both GnT I activities decreased in the following order: alpha1-3 alpha 1-6mannopentaose>alpha1-3 alpha 1-6mannotriose>alpha 1-3mannobiose>alpha 1-6mannobiose. These data suggest that two forms of GnT I exist in the testicular and epididymal fluids.
authors.affiliation: Department of Bioresource Science, Obihiro University of Agriculture and Veterinary Medicine, Inanda, Obihiro, Hokkaido 080-8555, Japan.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Nozaki
authors.forename: Tokihiro
authors.initials: T
authors.lastname: Matsuzawa
authors.forename: Tadashi
authors.initials: T
authors.lastname: Nakamura
authors.forename: Ikichi
authors.initials: I
authors.lastname: Arai
authors.forename: Tadasu
authors.initials: T
authors.lastname: Urashima
mesh_terms: D000818:Animals; D001826:Body Fluids / Q000737:chemistry / Q000201:enzymology*; D002118:Calcium; D002413:Cations, Divalent / Q000737:chemistry; D003035:Cobalt; D004822:Epididymis / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D008297:Male; D008345:Manganese; D008562:Membrane Glycoproteins / Q000378:metabolism; D017351:N-Acetylglucosaminyltransferases / Q000737:chemistry* / Q000378:metabolism; D009844:Oligosaccharides / Q000378:metabolism; D011134:Polysaccharides / Q000096:biosynthesis / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013094:Spermatozoa / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity; D013737:Testis / Q000201:enzymology*
chemical_list: D002413:Cations, Divalent; D008562:Membrane Glycoproteins; D009844:Oligosaccharides; D011134:Polysaccharides; C028569:oligomannoside; D003035:Cobalt; D008345:Manganese; D017351:N-Acetylglucosaminyltransferases; C024850:alpha-1,3-mannosyl-glycoprotein beta-1,2-N-acetylglucosaminyltransferase I; D002118:Calcium