Mannose-l-phosphate

Figure 3.119 Proposed biosynthetic pathway to mycosamine. (a) mannose-6-phosphate iso-merase (b) phosphomanno mntase (c) mannose-l-phosphate guanylyltransferase (d) PimJ (e) PimC (f) PimK.

Lukowitz W., Nickle T.C., Meinke D.W., Last R.L., Conklin P.L., and Somerville C.R. (2001). Arabidopsis cytl mutants are deficient in a mannose-l-phosphate guanylyltransferase and point to a requirement of N-linked glycosylation for cellulose biosynthesis. Proc. Natl. Acad. Sci. USA 98 2262-2267. 

Phosphorylase is specific with regard to its action upon < -D-glucose-l-phosphate the / -isomer cannot serve as a substrate for this enzyme. Neither can any other sugar ester be substituted for glucose-l-phosphate. a-L-Glucose-l-phosphate, maltose-l-phosphate, a-D-xylose-l-phosphate could not be polymerized to polysaccharide by potato phosphorylase. - The a-forms of D-mannose-l-phosphate and D-galactose-l-phosphate were not acted upon by muscle phosphorylase. ... 

The conversion of [2-3H]mannose-6-phosphate to [2-3H]mannose-l,6-bisphosphate in extracts from skin fibroblasts or leukocytes derived from patients is compared to controls. Calculation is performed by the TLC-analyser software Chromas 1.1 . 

These enzymes vary widely in secondary and tertiary structure.1273 Mannose-6-phosphate isomerase is a 45 kDa Zn2+-containing monomer. The larger 65 kDa L-fucose isomerase, which also acts on D-arabinose, is a hexameric Mn2+-dependent enzyme.1273 L-Arabinose isomerase of E. coli, which interconverts arabinose and L-ribulose, is a hexamer of 60-kDa subunits128 while the D-xylose isomerase of Streptomyces is a tetramer of 43-kDa subunits.129 The nonenzymatic counterpart of the isomerization catalyzed by the enzyme is the base-catalyzed Lobry deBruyn-Alberda van Ekenstein transformation (Eq. 13-25).130... 

Two of the most frequent monosaccharide components of bacterial polymers belonging to this group have been the subjects of articles in this Series. They are 3-deoxy-D-manno-2-octulosonic acid,247 a normal constituent of the core region of bacterial lipopolysaccharides that is also present in some other polymers, and N-acetylneuraminic acid,248 found in several capsular polysaccharides. Enolpyruvate phosphate serves as the precursor of the C-l-C-3 fragment of the monosaccharides, with D-arabinose 5-phosphate or 2-acetamido-2-deoxy-D-mannose 6-phosphate being an acceptor for transfer of the three-carbon unit. Characteristic, activated forms of these monosaccharides are the CMP derivatives. 

Figure 13. Plot of total ion current vj. emitter current for (A) mannose-1-phosphate, (B) mannose (OAc),rl-phosphate, and (C) mannose (OAc),-l-phosphate-O-...

L. Beljaars, G. Molema, B. Weert, H. Bonnema, P. Olinga, G. M. M. Groothuis, D. K. F. Meijer, and K. Poelstra, Albumin modified with mannose 6-phosphate a potential carrier for selective delivery of anti-fibrotic drugs to rat and human hepatic stellate cells, Hepatology 29 1486-1493 (1999). 

Figure 9. Radioactivity scan of a paper electrophoretogram of NaB[3Hreduced hydrolysate of f -galactosidase ("top) and a mixture of (l-galactosidase and mannose-6-phosphate ( bottom,). Experimental details are given in the text.

Figure 17-5. Synthesis of the mannose 6-phosphate recognition marker. R represents the high-mannose oligosaccharide of newly synthesized lysosomal enzymes. Reaction 1 is catalyzed by UDP-A,-acetylglucosamine lysosomal enzyme Ar-acetylglucosaminyl-1 -phosphotransferase. Reaction 2 is catalyzed by iV-acetylglucosamine-l-phosphodiester-iV-ace tylgluco saminidase.

T. neapolitana also adds mannose moieties onto the inositol rings, and this new phosphodiester, di-2-0-(3-mannosyl-di-myo-inositol-l,l -phosphate (Table 1) also appears to accumulate at high growth temperatures. However, DIP is still the major solute accumulated in T. neapolitana at supraoptimal growth temperatures (Martins et al., 1996). The addition of mannose to DIP produces a very unique phosphodiester, yet we know very little about why it is synthesized and accumulated. The involvement of these inositol solutes in thermoprotection... 

Jirtle, R.L. et al.. Increased mannose-6-phosphate insulin-like growth factor II receptor and transforming growth factor Pj levels during monoterpene-induced regression of mammary tumor. Cancer Res., 53, 3849, 1993. 

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