Purification and Characterization of N-Acetylglucosamine-6-phosphate Deacetylase from a Psychrotrophic Marine Bacterium, Alteromonas Species.

A psychrotrophic bacterium, strain Mct-9, which produced an N-acetylglucosamine-6-phosphate deacetylase, was isolated from a deep-seawater sample in the Mariana Trough. The Mct-9 strain was identified as Alteromonas sp. The native enzyme had a molecular mass of 164,000 Da, and was predicted to be composed of four identical subunits with molecular masses of 41,000 Da. The purified enzyme hydrolyzed N-acetylglucosamine (GlcNAc), GlcNAc-6-phosphate, and GlcNAc-6-sulfate. Considering the low K(m) and high k(cat)/K(m) for GlcNAc-6-phosphate, it probably acts as a GlcNAc-6-phosphate deacetylase in vivo. The enzyme was functional in the temperature range of 5 degrees to 70 degrees C and displayed optimal activity at 55 degrees C. The optimal temperature was higher than that of the deacetylase from the mesophilic bacterium Vibrio cholerae non-O1. The characteristics of the GlcNAc-6-phosphate deacetylase from Alteromonas sp. are unique among psychrotrophs and psychrophiles, whose intracellular enzymes are mostly thermolabile.