Characterization of a novel organophosphorus hydrolase from Nocardiodes simplex NRRL B-24074

Abstract

We characterized a novel organophosphorus hydrolase (OPH) activity expressed by Nocardiodes simplex NRRL B-24074, a member of a coumaphos-degrading microbial consortium from cattle dip waste. Like the previously characterized OPH from Nocardia sp. strain B-1 (NRRL B-16944), OPH activity in N. simplex is located in the cytoplasm and is expressed constitutively. The purified enzyme is monomeric, has a native molecular size of 45,000 Da and has a specific activity toward ethyl parathion of 33 μmole/min · mg protein. K m constants for the enzyme with the structurally related organophosphate pesticides ethyl parathion and EPN were 100 μM and 345 μM, respectively. Although OPH activity in extracts did not require the addition of divalent cations, the purified enzyme lost activity during dialysis against phosphate buffer and this activity could be restored after incubation in buffer containing either CoSO 4 or CuSO 4. Our results suggest that OPH activity in N. simplex is distinct from other known OPHs and that the responsible gene is unrelated to known genes.