SEQUENCE-ANALYSIS OF THE BETA-N-ACETYLHEXOSAMINIDASE GENE OF VIBRIO-VULNIFICUS - EVIDENCE FOR A COMMON EVOLUTIONARY ORIGIN OF HEXOSAMINIDASES

DNA cloned from the marine bacterium Vibrio vulnificus into Escherichi a coli HB101 can hydrolyze chitin oligomer analogs in the recipient. T he nucleotide sequence of the cloned DNA was determined and a single l ong open reading frame of 2541 base pairs (initiation codon through te rmination codon) was found. The nucleotide sequence predicts a gene pr oduct of 847 amino acids and a molecular mass of 94.3 kDa. In vitro tr anscription and translation analyses indicated a single protein of 94 kDa encoded by the cloned DNA. The gene product hydrolyzes methylumbel liferyl beta-D Conjugates of chitotriose, chitobiose, N-acetylglucosam ine, and N-acetylgalactosamine and has, therefore, been termed a beta- N-acetylhexosaminidase. The predicted protein shares a high degree of sequence similarity with the chitobiase of Vibrio harveyi and limited similarity with the alpha chain of human beta-hexosaminidase. Cluster analyses suggest a common evolutionary ancestor for all known hexosami nidase enzymes, with no detectable relationship to known chitinases.