Tryptophan glycoconjugates

Gutsche B, Gran C, Scheutzow D, Herderich M (1999) Tryptophan glycoconjugates in food and human urine. Biochem J 343 11-19... 

Shemesh O, Golbetz H, Kriss JP, Myers BD (1985) Limitations of creatinine as a filtration marker in glomeralonephro-pathic patients. Kidney Int 2 830-838 Starr R, Hostetter T, Hortin GL (2002) New markers for kidney disease. Clin Chem 48 1375-1376 Takahira R, Yonemura K, Yonekawa O et al. (2002) Tryptophan glycoconjugate as a novel marker of renal function. American J Med 110 192-197... 

A number of C- and Ai-linked tryptophan glycoconjugates were discovered as constituents of natural products [173,174,175,176]. Also tryptophan A-glucoside 27d has been detected for which Unverzagt et al. [177] reported a successful synthesis (O Scheme 27). With the help of 2-0-pivaloyl protection in glucosyl donor 27a the undesired acetal formation could be overcome thus with acceptor 27b Ai-glucoside 27c could be obtained and then transformed into target molecule 27d. 

Herraiz T., Galisteo J. Identification and occurrence of the novel alkaloid pentahydroxypentyl-tetrahydro-P-carboline-3-carboxylic acid as a tryptophan glycoconjugate in fruit juices and jams. Journal of Agricultural and Food Chemistry, 50 4690-4695 (2002). 

Garcia, A., Lenis, L.A., Jimenez, C Debitus, C., Quinoa, E., and Riguera, R. (2000) The occurrence of the human glycoconjugate C -a-D-mannosylpyranosyl-L-tryptophane in marine ascidians. Org. Lett., 2, 2765-2767. 

A C-glycoconjugate of L-tryptophan with a-D-mannose, considered specific to the human species, was recently found in Pharyngodictyon caulijlos (Polyclinidae) and Lep-toclinides dubius (Didemnidae), and its N-methyl derivative has been identified in another polyclinid, Ritterella rete (Carcia et al, 2000). 

In humans, such glycoconjugates are involved in the post-translational modification of proteins, but this is usually achieved by the formation of an O- or N-glycosyla-ted derivative. It was not until recently that C-glycosylated derivatives were shown to be involved in the metabolism of tryptophan, and the presence of such glycoconjugates in three species of ascidians implies the existence of a C-mannosyltransferase in these invertebrates, which may become a new source of C-glycoconjugates (see above and Carcia et al, 2000). 

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