A　chitinase　gene　from　Serratia　marcescens　was　cloned　and　expressed　in　Escherichia　coli　BL21(DE3)　and　the　properties　of　recombinant　chitinase　rCHI-2　were　characterized.　The　optimum　catalytic　pH　of　rCHI-2　was　6.0.　It　was　stable　in　the　pH　range　of　6.0-9.0　and　could　maintain　more　than　90%　of　its　relative　enzyme　activity　after　incubation　at　37　degrees　C　for　1　h.　The　optimum　catalytic　temperature　of　the　enzyme　was　55　degrees　C　and　85%　of　enzyme　activity　was　remained　after　incubation　at　45　degrees　C　for　1　h.　The　activation　energy　of　the　thermal　inactivation　of　the　enzyme　was　10.9　kJ/mol　and　the　Michaelis-Menten　constant　was　3.2　g/L.　The　purified　rCHI-2　was　found　to　be　highly　stable　at　45　degrees　C　with　half-life　(t(1/2))　of　289　min　and　thermodynamic　parameters　Delta　H*,　Delta　G*　and　Delta　S*　revealed　high　affinity　of　rCHI-2　for　chitin.　Hg2+　was　found　to　be　able　to　inhibit　the　enzyme　activity　reversibly,　while　IC50　and　inhibition　constant　of　Hg2+　on　the　enzyme　were　34.8　mu　mol/L　and　44.6　mu　mol/L,　respectively.　Moreover,　rCHI-2　could　specifically　hydrolyze　colloidal　chitin　into　GlcNAc(2)　as　the　major　product.