Membrane‐bound glucosamine acetyltransferase in coleoptile segments of Avena sativa

Abstract

The in vivo metabolism of D‐[U‐14C]glucosamine and the in vitro properties of glucosamine acetyltransferase (EC 2.3.1.3), the first committed enzyme in the metabolism of exogenously supplied D‐glucosamine, were studied in coleoptile segments of Avena sativa L. cv. Sole II. D‐[U‐14C]glucosamine was taken up by oat coleoptile segments and sequentially metabolised to radioactive N‐acetylglucosamine, N‐acetylglucosamine 6‐P, N‐acetylglucosamine 1‐P, UDP‐N‐acetylglucosamine and UDP‐N‐acetylgalactosamine. In addition, N‐acetylglucosamine residues were incorporated into glycoproteins and glycolipids of the cells. All glucosamine acetyltransferase activity was found to be membrane‐bound. The enzyme was solubilized by either digitonin or CHAPS. The specificities and the kinetics of the membrane‐bound and soluble glucosamine acetyltransferase were determined. The effects of ions, nucleotides, nucleoside diphosphate amino sugars, coenzymes and group‐specific chemical probes on the rate of membrane‐bound and CHAPS‐solubilized enzyme were investigated. Our data indicate that UDP‐N‐acetylglucosamine and UDP‐N‐acetylgalactosamine do not exert a feed‐back control on the glucosamine acetyltransferase either in vivo or in vitro. Further, some nucleotides and the metal ions Cu2+, Zn2+, Fe2+, Fe3+ and Co2+ affect the activity of the enzyme in vitro.

Characterization of a Glucosamine/Glucosaminide N -Acetyltransferase of Clostridium acetobutylicum

“…GlmA shows only very weak amino acid sequence homology with characterized enzymes of the GNAT family but exhibits an overall identity of up to 36% with predicted N-acetyltransferases of various species of the Clostridium and Thermoanaerobacter genera, including the two extremely thermophilic ethanol-and acetateproducing organisms T. mathranii strain A3 and T. tengcongensis strain MB4 (14,34). GlcN N-acetyltransferase activity has been identified in crude pigeon liver extracts and membrane fractions isolated from oat coleoptile segments, which are so far the only descriptions of such an enzymatic activity (9,21). This is thus the first report of a cloned and characterized GlcN N-acetyltransferase (EC 2.3.1.3).…”

Methodological approach for the study of glycoconjugates inLeptolyngbyaVRUC 135

“…It has been reported that the metabolism of D-[U-14 C]glucosamine in Calluna seedlings (Piro et al 1988), in excised bean and corn root tips (Roberts 1970) and in Koliella antarctica (Lenucci et al 2006), starts with the formation of only radioactive N-acetyl-D-glucosamine. In oat coleoptiles, an enzyme acetylating D-glucosamine has been reported (Piro et al 1994). Nevertheless, enzymes phosphorylating D-glucosamine have been isolated from yeast (Brown 1951) and higher plants (Saltman 1953).…”

Biosynthesis and characterization of glycoproteins inKoliella antarctica(Klebsormidiales, Chlorophyta)

“…14 C]glucosamine is sequentially metabolized by K. antarctica cells into N-acetylglucosamine, N-acetylglucosamine 6-phosphate, N-acetylglucosamine 1-phosphate, UDP-N-acetylglucosamine and UDP-N-acetylgalactosamine, according to the pathway reported in land plants (Roberts, 1970;Piro et al, 1988Piro et al, , 1994.…”

“…Immuno-recognition with SBA and HPA was used to reveal the presence of terminal residues of N-acetylgalactosamine. (Roberts, 1970;Piro et al, 1988Piro et al, , 1994. The D-[U-14 C]glucosamine, exogenously supplied to the microalga investigated, is first acetylated to N-acetylglucosamine and then phosphorylated to N-acetylglucosamine 6-P.…”

“…The D-[U-14 C]glucosamine, exogenously supplied to the microalga investigated, is first acetylated to N-acetylglucosamine and then phosphorylated to N-acetylglucosamine 6-P. In oat coleoptile segments, a membranebound glucosamine acetyltransferase has been reported (Piro et al, 1994).…”