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-acetylglucosa mine-6-phosphate deacetylase, was isolated from a deep-seawater sample in t he Mariana Trough. The Mct-9 strain was identified as Alteromonas sp. The n ative enzyme had a molecular mass of 164,000 Da, and was predicted to be co mposed of four identical subunits with molecular masses of 41,000 Da. The p urified enzyme hydrolyzed N-acetylglucosamine (GlcNAc), GlcNAc-6-phosphate, and GlcNAc-6-sulfate. Considering the low K-m and high k(cat)/K-m for GlcN Ac-6-phosphate, it probably acts as a GlcNAc-6-phosphate deacetylase in viv o. The enzyme was functional in the temperature range of 5 degrees to 70 de grees C and displayed optimal activity at 55 degrees C. The optimal tempera ture was higher than that of the deacetylase from the mesophilic bacterium Vibrio cholerae non-Ol. The characteristics of the GlcNAc-6-phosphate deace tylase from Alteromonas sp. are unique among psychrotrophs and psychrophile s, whose intracellular enzymes are mostly thermolabile.