An endo-xylanase gene (xynD) encoding xylanase VI (58 kDa) of Aeromonas caviae ME-1 was cloned and expressed in Escherichia coli, The xynD gene encodes a 564 amino acid precursor (62,083 Da) and 531 amino acid mature enzyme (58,469 Da), The enzyme consists of two domains bridged by a glycine-rich linker. The N-terminal catalytic domain (392 amino acids) sequence is homologous neither to family F nor family G (families 10, 11) enzymes, into which almost all known xylanases are categorized. However, it has 41% identity with XynA of Erwinia chrysanthemi, The C-terminal domain (125 amino acids) shows homology to conserved domains in xylanase (XYLB), arabino-furanosidase (XYLC), and acetylxylan-esterase (XYLD) of Pseudomonas fluorescens subsp. cellulosa, but its function is unknown. The E. coli transformant produced 58-, 48-, 45-, and 43-kDa active xylanases as the result of C-terminal proteolytic truncation.