Mh. Wu et Ra. Laine, Sequence of the V. parahaemolyticus gene for cytoplasmic N,N '-diacetylchitobiase and homology with related enzymes, J BIOCHEM, 125(6), 1999, pp. 1086-1093
The nucleotide sequence of the gene encoding the cytoplasmic N,N'-diacetylc
hitobiase [EC 3.2.1.14] from Vibrio parahaemolyticus (ATCC #27969) has been
determined, The deduced peptide sequence of this unusual P-hexosaminidase
surprisingly shows minimum evolutionary relationship to two other reported
N,N'-diacetylchitobiases from vibrios, except in highly conserved regions w
hich are also homologous to lysosomal P-hexosaminidases from eukaryotes inc
luding humans. In contrast, the two other P-hexosaminidases from vibrios wi
th reported sequences are much more closely related to each other. This nov
el 85 kDa cytoplasmic glycosyl hydrolase with restricted specificity partic
ipates in the high level utilization of chitin-derived 2-deoxy-2-acetamido-
D-glucose (GlcNAc) by vibrios as one of two parallel pathways for the metab
olism of N,N'-diacetylchitobiose .These pathways use chitin-binding protein
s for the adherence of the bacterial chitinase to the substrate, and an ext
racellular chitinase and a periplasmic chitodextrinase to produce N,N'-diac
etylchitobiose, The Tr, parahaemolyticus cytoplasmic N,N,N'-diacetyl-chitob
iase reported herein appears to be a unique protein, lacking a signal seque
nce, and genetically distant from other known chitinoclastic beta-N,N'-diac
etyl-hexosaminidases. This is consistent with its limited substrate specifi
city to small GlcNAc terminated oligosaccharides and its cytoplasmic rather
than periplasmic localization.