Title : Purification and chemical characterization of
beta-trace protein from human cerebrospinal fluid: its identification as
prostaglandin D synthase
Abstract :
- beta-Trace protein from pooled human CSF was purified to homogeneity
- An apparent molecular mass of 23-29 kDa was determined for the polypeptide on sodium dodecyl sulfate-polyacrylamide gel electrophoresis
- Amino-terminal sequencing of the polypeptide yielded the unique amino acid sequence APEAQVSVQPNFQQDKFLGRWFSA
- Alignment of amino acid sequences obtained from tryptic peptides with the sequence previously deduced from a cDNA clone isolated by other investigators allowed the identification of beta-trace protein as prostaglandin D synthase [ prostaglandin-H2 D-isomerase ; (5Z, 13E)-(15S)-9 alpha, 11 alpha-epidioxy-15-hydroxyprosta-5,13-dienoate D-isomerase ; EC 5.3.99.2]
- A conservative amino acid exchange ( Thr instead of Ser ) was detected at amino acid position 154 of the beta-trace polypeptide chain in the corresponding tryptic peptide
- The two N-glycosylation sites of the polypeptide were shown to be almost quantitatively occupied by carbohydrate
- Carbohydrate compositional as well as methylation analysis indicated that Asn29 and Asn56 bear exclusively complex-type oligosaccharide structures (partially sialylated with alpha 2-3- and/or alpha 2-6-linked N-acetylneuraminic acid) that are almost quantitatively alpha 1-6 fucosylated at the proximal N-acetylglucosamine; approximately 70% of these molecules contain a bisecting N-acetylglucosamine.
- Agalacto structures as well as those with a peripheral fucose are also present