Zn. Senwo et Ma. Tabatabai, Aspartase activity in soils: effects of trace elements and relationships to other amidohydrolases, SOIL BIOL B, 31(2), 1999, pp. 213-219
The enzyme aspartase (L-aspartase ammonia-lyase, EC 4.3.1.1) catalyzes the
hydrolysis of L-aspartate to produce fumarate and NH3. This enzyme is invol
ved in N mineralization in soils. Recently, the activity of this enzyme was
detected in soils, and a method was developed for its assay. The method wa
s used in studies of the effects of the salts of 24 trace elements on the a
ctivity of aspartase in three field-moist soils and their air-dried counter
parts. At 5 mu mol g(-1) soil, all the trace elements inhibited aspartase a
ctivity in the soils. With most of the elements, greater inhibition was fou
nd in air-dried than in field-moist soils. Among the trace elements studied
, Ag(I) and Hg(II) were the most effective inhibitors of aspartase activity
; >85% when added at 5 mu mol g(-1) soil. The least inhibition (12%) was wi
th Ni added to the field-moist Harps soil and the greatest (98%) was with A
g(I) in the air-dried Weller soil. Aspartase activity was significantly cor
related with the contents of organic C (r = 0.85*** P < 0.001), total N (r
= 0.73***) and clay (r = 0.44*, P < 0.05) but not with the content of sand
or the pH of 27 surface soils examined, including the three soils used in t
he studies of the effects of trace elements. The activity of this enzyme in
soils was significantly correlated with the activities of asparaginase (I
= 0.94***), glutaminase (r = 0.88***), urease (r = 0.80***) and amidase (I
= 0.44*). (C) 1998 Elsevier Science Ltd. All rights reserved.