User:Elizabeth Schneider
From Proteopedia
N-acetylglucosamine phosphotransferase Elizabeth Schneider and Samantha Templeton; Students; Erskine College, Due West, SC, United States
N-acetylglucosamine (GlcNAc) phosphotransferase is a cis-Golgi-localized enzyme that recognizes the specific protein sequence in newly synthesized lysosomal enzymes and transfers phosphorylated GlcNAc groups [1]. This enzyme is hexameric, composed of two alpha, two beta, and two gamma subunits [2].
The alpha and beta subunits result from a single cDNA and formed by proteolysis at a LYS-ASP bond on the alpha/beta precursor [3]. The alpha and beta subunits are encoded by the GNPTAB gene, but the gamma subunit is encoded independently by the GNPTG gene, making GlcNAc an exception to the Garrod-Beadle principle that one enzyme is encoded by one gene [4,5]. Mucolipidosis II is a phenotypic disease caused by disruptions of the alpha and beta subunits, as patients with the disease had either absent or reduced alpha/beta transcription; however, all patients had normal gamma subunit levels [4,6]. This suggests that the alpha and/or the beta subunit contains enzymatic qualities.
Post-translational modifications such as interchain and intramolecular disulfide bonds may occur via GlcNAc-phosphotransferase in the cytoplasm outside of the nucleus, including the protein glycosylation on serine and threonine residues. Any imbalance of phosphorylation can lead to diseases including cancer, diabetes, and neurodegenerative diseases. Management of phosphorylation and other modifications performed by GlcNAc-phosphotransferase can allow for better diagnoses and treatments of such diseases [7].
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References [1]. Bioconjugate Chem., 2014, 25 (6), pp 1025–1030 [2]. Bao, M., Elmendorf, B. J., Booth, J. L., Drake, R. R., Canfield, W. M. Bovine UDP-N-acetylglucosamine:lysosomal-enzyme N-acetylglucosamine-1-phosphotransferase: II. Enzymatic characterization and identification of the catalytic subunit. J. Biol. Chem. 271: 31446-31451, 1996. [3]. Canfield, W. M., Bao, M., Pan, J., Brewer, A. D. K., Pan, H., Roe, B., Raas-Rothschild, A. Mucolipidosis II and mucolipidosis IIIA are caused by mutations in the GlcNAc-phosphotransferase alpha/beta gene on chromosome 12p. Am. J. Hum. Genet. 63: A15 only, 1998. [4]. Hartz, P. A. N-Acetylglucosamine-1-phosphotransferase, Alpha/Beta Subunits; GNPTAB. [5]. Kudo, M., Bao, M., D'Souza, A., Ying, F., Pan, H., Roe, B. A., Canfield, W. M. The alpha- and beta-subunits of the human UDP-N-acetylglucosamine:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase are encoded by a single cDNA. J. Biol. Chem. 280: 36141-36149, 2005. [6]. Canfield, W. M., Bao, M., Pan, J., Brewer, A. D. K., Pan, H., Roe, B., Raas-Rothschild, A. Mucolipidosis II and mucolipidosis IIIA are caused by mutations in the GlcNAc-phosphotransferase alpha/beta gene on chromosome 12p. Am. J. Hum. Genet. 63: A15 only, 1998. [7]. Lodish, H. F., et al. Molecular cell biology, 8th ed.; W.H. Freeman-Macmillan Learning: New York, 2016. [8]. Q9UJJ9 N-acetylglucosamine-1-phosphotransferase subunit gamma. Swiss-Model. 2019. [9]. RCSB Protein Data Bank. NMR structure of the 140-315 fragment of the N-acetylglucosamine-1-phosphotransferase, alpha and beta subunits.
