The Completed Sequence of a Glycopeptide Obtained from Taka-amylase A*

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Abstract
The sequence of the components of a Taka-glycopeptide (TAA-GP) obtained from Taka-amylase A [EC 3.2.1.1] was determined using O-methylation, partial acetolysis and periodate oxidation techniques. The polyaldehyde produced by periodate oxidation of the TAA-GP was reduced with sodium borohydride to the corresponding polyalcohol (D1-GP-polyalcohol). 0-Methylation of D1-GP-polyalcohol followed by methanolysis gave 1,3-di-O-methyl-glycerol and methyl 2,4-di-O-methyl-α-mannoside as judged by gas chromatography. Methanolysis of O-methylated TAA-GP yielded methyl 2,3,4,6-tetra-O-methyl-α-mannoside, methyl 3,4,6-tri-O-methyl-ar-mannoside, and methyl 2,4-di-O-methyl-α-mannoside in an approximate ratio of 3 : 1 : 2. The results of gas chromatographic analyses of the methanolysates obtained from the O-methylated D1-GP-polyalcohol and O-methylated TAA-GP, combined with the results obtained previously, permitted deduction of the linking points of mannose residues in TAA-GP, except a single residue linked to position Ci of one of the three non-reducing end residues. Partial acetolysis of 1,6-linkages gave mannose and mannopyranosyl-(l–3)-man-nopyranose together with the rest of the molecule which was resistant to acetolysis. The carbohydrate-peptide linkage was elucidated to be β-anomeric as judged from paper chromatographic study of the smallest glycopeptide composed of one mole each of asparagine and N-acetyl-glucosamine.

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