Comment on "The first description of an archaeal hemicellulase: the xylanase from Thermococcus zilligii strain AN1": evidence that the unique N-terminal sequence proposed comes from a maltodextrin phosphorylase.

Abstract

Uhl and Daniel reported in this journal in 1999 (Extremophiles 3:263-267) the characterization of the first archaeal hemicellulase with a unique N-terminal sequence showing no homology with any xylanase or other protein from the databases. A genomic library of the chromosomal DNA of Thermococcus zilligii strain AN1 was screened by using a degenerate probe deduced from the N-terminal sequence. A positive clone was identified, and an amino acid sequence analysis revealed that the N-terminal sequence from this protein and the N-terminal sequence from the putative xylanase of T. zilligii were identical. However, the comparison of the amino acid sequence of the protein with sequences in the main protein databases revealed significant similarities with maltodextrin phosphorylases. In conclusion, it is likely that the N-terminal sequence proposed by Uhl and Daniel is not that of the T. zilligii xylanase, but corresponds to an archaeal T. zilligii maltodextrin phosphorylase.