Arthrobacter sp. strain PY1, a bacterium having the ability to degrade 1.3-dichlotopropanol (1.3-DCP), was isolated from a soil sample of a chemical plant. Strain PY1 degraded 1000 mg/l (7.75 mM) of 1.3-DCP completely within 7 days, and the ability was elevated by acclimatization up to 4000 mg/l/week. Addition of nutrients such as peptone, glucose or glycerol showed no or slight effect on the degrading activity. These results suggest that strain PY1 is a useful organism in a biological control system for 1,3-DCP pollution. The ability to degrade 1.3-DCP was induced by addition of 1.3-DCP to the culture of strain PY1. A 1.3-DCP-degrading enzyme (Deh-PY1) was purified from the cytoplasmic fraction of strain PY1 by fractionation with ammonium sulfate, hydrophobic chromatography and anion exchange chromatography. Purified Deh-PY1 is a tetramer of a homogeneous subunit having a molecular weight of 20 kDa. Analysis of the N-terminal amino acid sequence of Deh-PY1 showed that the 31 residues were quite similar to those of known 1.3-DCP-dehalogenases of other organisms. Arthrobarter sp. strain AD2 and Corynebacterium sp. strain N-1074, although some differences in composition or enzymatic characteristics were observed. The Km value and Vmax of Deh-PY1 were 2.67 mM and 7.81 mumol/min/mg, respectively. and the optimum reaction temperature and pH were 40-50degreesC and 9.5-10.5.