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Amidase Activity in Soils: I. Method of Assay
Author(s) -
Frankenberger W. T.,
Tabatabai M. A.
Publication year - 1980
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/sssaj1980.03615995004400020016x
Subject(s) - amidase , chemistry , acetamide , hydrolysis , substrate (aquarium) , amide , toluene , enzyme assay , chromatography , nuclear chemistry , enzyme , organic chemistry , oceanography , geology
Amidase [acylamide amidohydrolase, EC (Enzyme Commission) 3.5.1.4] is the enzyme that catalyzes the hydrolysis of amides and produces the corresponding carboxylic acid and ammonia. The detection of this enzyme in soils is reported, and a simple, sensitive, and precise method to assay amidase is described. The method involves determination by steam distillation of the NH 4 + produced by amidase activity when soil is incubated with buffered (0.1 M THAM, pH 8.5) amide solution and toluene at 37°C. The amide compounds studied included formamide, acetamide, and propionamide. The procedure developed gives quantitative recovery of NH 4 ‐N added to soils and does not cause chemical hydrolysis of the substrates. Results showed that this soil enzyme has its optimum activity at buffer pH 8.5 and is inactivated at temperatures above 60°C. By varying the substrate concentration it was found that the initial velocity of the amidase reaction is optimum at 0.05 M substrate. The initial rates of NH 4 ‐N released obeyed zero‐order kinetics. Steam sterilization destroyed, and formaldehyde, sodium fluoride, and sodium arsenite inhibited, amidase activity in soils. Assay of amidase activity in the absence of toluene indicated that acetamide and propionamide may induce the synthesis of this enzyme by soil microorganisms.