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Michaelis Constants of Urease in Soils and Soil Fractions
Author(s) -
Tabatabai M. A.
Publication year - 1973
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1973.03615995003700050024x
Subject(s) - urease , soil water , chemistry , incubation , substrate (aquarium) , michaelis–menten kinetics , silt , incubation period , environmental chemistry , zoology , soil science , enzyme assay , enzyme , geology , ecology , biochemistry , biology , paleontology
Studies to determine the Michaelis constant ( K m value) for urease activity in Iowa surface soils showed that the value obtained for the activity of this enzyme was different for different soils. When the method used to determine K m did not involve shaking of the soil‐substrate mixtures, the K m value for urease activity ranged from 1.3 × 10 ‐3 M to 7.0 × 10 ‐3 M . Shaking the soil‐substrate mixtures during incubation decreased the K m value obtained, and statistical analysis showed that this value was significantly correlated with organic C and total N. There was no significant correlation, however, between K m value of the urease activity and other soil properties studied (pH, percentage clay, percentage silt, percentage sand). The maximum enzyme reaction velocity ( V max value) for urease activity in soils was markedly different for different soils and always increased when the soil‐substrate mixtures were shaken during incubation. The V max values obtained from static and shaking incubation techniques were significantly correlated with organic C, total N, and clay content. Results reported show that the K m value of urease in soils is similar to that of urease in soil fractions and is nearly two orders of magnitude lower than the previously reported K m value for this enzyme in soils.