Synthesis of GDP-L-fucose by the human FX protein.
FX is a homodimeric NADP(H)-binding protein of 68 kDa, first identified in human erythrocytes, from which it was purified to homogeneity. Its function has been unrecognized despite partial structural and genetic characterization. Recently, on the basis of partial amino acid sequence, it proved to be the human homolog of the murine protein P35B, a tumor rejection antigen. In order to address the biochemical role of FX, its primary structure was completed by cDNA sequencing. This sequence revealed a significant homology with many proteins from different organisms. Specifically, FX showed a remarkable similarity with a putative Escherichia coli protein, named Yefb, whose gene maps in a region of E. coli chromosome coding for enzymes involved in synthesis and utilization of GDP-D-mannose. Accordingly, a possible role of FX in this metabolism was investigated. The data obtained indicate FX as the enzyme responsible for the last step of the major metabolic pathway resulting in GDP-L-fucose synthesis from GDP-D-mannose in procaryotic and eucaryotic cells. Specifically, purified FX apparently catalyzes a combined epimerase and NADPH-dependent reductase reaction, converting GDP-4-keto-6-D-deoxymannose to GDP-L-fucose. This is the substrate of several fucosyltranferases involved in the correct expression of many glyconjugates, including blood groups and developmental antigens.
Tonetti
M
M
Institute of Biochemistry, University of Genova, and Advanced Biotechnology Center, Viale Benedetto XV, 1, 16132 Genova, Italy.
Sturla
L
L
Bisso
A
A
Benatti
U
U
De Flora
A
A
D000595:Amino Acid Sequence; D000818:Animals; D000954:Antigens, Surface / Q000737:chemistry; D001483:Base Sequence; D001798:Blood Proteins / Q000737:chemistry / Q000378:metabolism; D017173:Caenorhabditis elegans; D002238:Carbohydrate Epimerases; D006528:Carcinoma, Hepatocellular; D002352:Carrier Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D003600:Cytosol / Q000378:metabolism; D018076:DNA, Complementary; D004912:Erythrocytes / Q000378:metabolism*; D004926:Escherichia coli; D006154:Guanosine Diphosphate Fucose / Q000378:metabolism*; D006155:Guanosine Diphosphate Mannose / Q000378:metabolism; D006801:Humans; D007658:Ketone Oxidoreductases; D008113:Liver Neoplasms; D051379:Mice; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009419:Nerve Tissue Proteins / Q000737:chemistry; D016133:Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D050827:Syntaxin 1
D000954:Antigens, Surface; D001798:Blood Proteins; D002352:Carrier Proteins; D018076:DNA, Complementary; D009419:Nerve Tissue Proteins; D050827:Syntaxin 1; D006154:Guanosine Diphosphate Fucose; D006155:Guanosine Diphosphate Mannose; C028277:TSTA3 protein, human; D007658:Ketone Oxidoreductases; D002238:Carbohydrate Epimerases