Abstract
An assay was developed to measure the activity of the enzyme L-cysteine desulfhydrase (CDA) in an agricultural loam soil. The optimum temperature for CDA in this soil was 60 degrees C and the optimum pH for CDA in the soil was 8.5. CDA in the soil required the addition of pyridoxal phosphate to exhibit its maximum activity. However since no pyridoxal phosphate was found in this soil it is likely that activity of this enzyme in the soil will be limited by the lack of this cofactor. Our studies illustrate the important point that not all enzymes which can be assayed in soils under laboratory conditions will function in the environment, since some, as in the case of CDA, will be limited by a lack of an essential co-factor.