Phosphoglycosylation of a secreted acid phosphatase from Leishmania donovani

The secreted acid phosphatase (SAcP) of L.donovani is a heterogeneous glyco protein that displays a wide array of N- and O-linked glycosylations, The O -linked sugars are of particular interest due to their similarity to the ph osphoglycan structures of the major lipophosphoglycan surface antigen and r eleased phosphoglycan (Turco et at, 1987; Greis et al,, 1992), This study d escribes a structural analysis of the SAcP O-linked glycosylations using ma ss spectroscopy, amino acid sequencing, and enzymatic carbohydrate sequenci ng. Analysis of glycan chain lengths and peptide glycosylation site distrib ution was performed, revealing that the average O-linked structure was simi lar to 32 repeat units in length. Amino acid sequence analysis of glycosyla ted peptides showed that phosphoglycosylations did not occur randomly but w ere localized to specific serine residues within an array of degenerate ser ine/threonine-rich repeat sequences localized in the C-terminus. No evidenc e was obtained for modification of threonine residues. The observed pattern suggested that a consensus sequence may exist for localization of phosphog lycan structures.