GlcNAc-1-phosphotransferase

Pseudo-Hurler polydystrophy is another genetic disease closely related to I-ceU disease. It is a milder condition, and patients may survive to adulthood. Smdies have revealed that the GlcNAc phosphotransferase involved in I-cell disease has several domains, including a catalytic domain and a domain that specifi-... 

An alternative processing pathway is used by proteins that wUl traffic to the lysosome. GlcNAc-phosphotransferase adds... 

Scheme 2. Rationalization of inhibitory activity of the tunicamycins as a mimic of the transition state of the UDP-GlcNAc phosphotransferase reaction...

An important additional pathway is indicated in reactions I and II of Figure 47-9. This involves enzymes destined for lysosomes. Such enzymes are targeted to the lysosomes by a specific chemical marker. In reaction I, a residue of GIcNAc-1-P is added to carbon 6 of one or more specific Man residues of these enzymes. The reaction is catalyzed by a GIcNAc phosphotransferase, which uses UDP-GlcNAc as the donor and generates UMP as the other product ... 

CDG-Ij UDP-GlcNAc dolichol phosphate N-acetylglucosamine-phosphotransferase 1 DPAGT1 1 lq23 608093... 

Some hereditary diseases are characterized by lack of two or more lysosomal enzymes. In I-ceII disease (mucolipidosis II), which resembles the Hurler syndrome, at least ten enzymes are absent or are present at much reduced levels.350,361 The biochemical defect is the absence from the Golgi cisternae of the N-acetylglucosaminyl phosphotransferase that transfers P-GlcNAc units from UDP-GlcNAc onto mannose residues (Eq. 20-22) of glycoproteins marked for use in lysosomes. 

Generally, phosphotransferase is assayed using a-methylmannoside as acceptor. After incubation, the reaction is terminated, and the phosphodiester product of the transfer reaction, (i.e., [l4C or 3H]GlcNac-a-l-phospho-6-mannose-a-l-methyl) is chromatographically separated from the reaction components, and the radioactivity is determined. The general reaction scheme is... 

Chauvin et al. 1994 Bouma and Roseman 1996), whereas the disaccharide is taken up unchanged. The further catabolism of (GlcNAc)2 gives A,A -diacetylchitobiose, which can be catabolized by Escherichia coli and is transported/phosphorylated by the phosphoenolpyruvateiglycose phosphotransferase systems (Keyhani et al. 2000b), the major subject to address in-depth in the whole pathway of the chitin degrading mechanism in Vibrios. 

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