Rhodanese Activity of Soils

Abstract

Abstract The detection of rhodanese (enzyme catalyzes the formation of SCN ‐ from S 2 O 3 2‐ and CN ‐ ) in soils is reported, and a simple method of assaying rhodanese activity in soils is described. This method involves colorimetric determination of the SCN ‐ produced by rhodanese activity when soil is incubated with buffered (0.05 M THAM, pH 6.0) S 2 O 3 2‐ and CN ‐ solutions and toluene at 37°C for 1 hour. The method developed is rapid, sensitive, and precise. The procedure used to extract SCN ‐ stops rhodanese activity in soils and gives quantitative recovery of the SCN ‐ formed. Results showed that steam sterilization and formaldehyde inhibit, sulfate and chloride activate, and toluene has no effect on rhodanese activity in soils. The initial rates of SCN ‐ formation obeyed zero‐order kinetics; in one soil, the rate slowed with time of incubation. The temperature dependence of the rate constant conformed to the Arrhenius equation up to the point of enzyme inactivation (65°C). The activation energy of rhodanese activity of the eight soils studied ranged from 5,160 to 8,110 (avg. 6,690) calories/mole. Studies of other properties of rhodanese activity in soils are reported.