PROPERTIES OF POLY(3-HYDROXYBUTYRATE) DEPOLYMERASE FROM A MARINE BACTERIUM, ALCALIGENES-FAECALIS AE122

Alcaligenes faecalis AE122 that used poly(3-hydroxybutyrate) (PHB) as a sole source of carbon was newly isolated from a coastal seawater sam ple. The strain required seawater for growth on PHB as well as in a nu trient broth, in which seawater could be replaced by an appropriate co ncentration of NaCl. PHB depolymerase was purified to homogeneity from the culture supernatant of A. faecalis AE122 by sodium dodecyl sulfat e-polyacrylamide gel electrophoresis. The enzyme consisted of a monome r subunit with a molecular mass of 95.5 kDa. The N-terminal amino acid sequence was GAWQNNLAGGFNKV. The dimeric and trimeric esters of 3-hyd roxybutyrate were the main hydrolysis products of the purified enzyme. The enzyme was most active at pH 9.0 and 55 degrees C and was inhibit ed by phenylmethylsulfonyl fluoride. Several cations in seawater great ly enhanced the enzyme activity.