FACTORS AFFECTING RHODANESE ACTIVITY IN SOILS1

Abstract

Studies of the effects of various soil pretreatments on soil rhodanese activity showed that storage at −20°C or 5°C is a satisfactory method of preserving field-moist samples for assay of rhodanese activity. Air-drying of field-moist soils resulted in a marked decrease (average, 44 percent) of rhodanese activity. Rhodanese activity decreased markedly with depth in five soil profiles studied. This decrease was associated with a decrease in organic C. Preincubation of six soils for 24 h and 48 h with glucose (0.1 percent) resulted in average rhodanese activity increase of 9 and 23 percent, respectively. When the buffer was made to contain 1mM with respect to inorganic compounds tested, NaNO2, NaN3, Na2SO4, NaF, and NaCl activated rhodanese activity in soils, and NaNO3, Na2SO3, Na2S, KH2PO4, and NaHCO3 inhibited it.With the exception of Zn, all the other 15 trace elements studied (50 ±mole/g of soil) inhibited rhodanese activity; Zn ions activated this enzyme in soils. The percentage inhibition of rhodanese activity by trace elements varied considerably among the three soils studied. The trace elements that showed average inhibition of ≥50 percent, however, were: Mn(II), Sn(II), Ni(II), Cr(III), B(III), Al(III), As(III), Se(IV), V(IV), Ti(IV), As(V), W(VI), and Mo(VI). Studies of the effects of various soil pretreatments on soil rhodanese activity showed that storage at −20°C or 5°C is a satisfactory method of preserving field-moist samples for assay of rhodanese activity. Air-drying of field-moist soils resulted in a marked decrease (average, 44 percent) of rhodanese activity. Rhodanese activity decreased markedly with depth in five soil profiles studied. This decrease was associated with a decrease in organic C. Preincubation of six soils for 24 h and 48 h with glucose (0.1 percent) resulted in average rhodanese activity increase of 9 and 23 percent, respectively. When the buffer was made to contain 1mM with respect to inorganic compounds tested, NaNO2, NaN3, Na2SO4, NaF, and NaCl activated rhodanese activity in soils, and NaNO3, Na2SO3, Na2S, KH2PO4, and NaHCO3 inhibited it. With the exception of Zn, all the other 15 trace elements studied (50 ±mole/g of soil) inhibited rhodanese activity; Zn ions activated this enzyme in soils. The percentage inhibition of rhodanese activity by trace elements varied considerably among the three soils studied. The trace elements that showed average inhibition of ≥50 percent, however, were: Mn(II), Sn(II), Ni(II), Cr(III), B(III), Al(III), As(III), Se(IV), V(IV), Ti(IV), As(V), W(VI), and Mo(VI). © Williams & Wilkins 1978. All Rights Reserved.