Range and assay of soil enzymes

Soil enzymes most frequently studied are oxidoreductases (especially dehydrogenases, catalase and peroxidase) and hydrolases (especially invertase, proteinases, phosphatases and urease). A few studies measure activities attributable to transferases and lyases no investigations of isomerases and ligases have been reported (Table 1). 

Because most soil enzyme studies deal with crude soil suspensions, or at best partially-purified soil extracts, care must be exercised in assigning an activity to the action of a particular enzyme. This note of caution is perhaps justified by considering the conversion in soils of urea to NH4 and CO2. Urea is an important nitrogenous fertilizer and is a major constituent of the urine of grazing animals, and studies of urea hydrolysis have dominated the soil enzyme literature. It is widely assumed that urea hydrolysis is catalysed by urease (urea amidohydrolase, EC 3.5.1.5). Studies have compared the kinetics and inhibition of urea hydrolysis by soils and by purified ureases, mainly from jack bean, Canavalia ensiformis, Jack bean urease catalyses urea hydrolysis by a pathway in which carbamate is an intermediate. 

10 catechol oxidase, p-diphenol oxidase, ascorbate oxidase 

1 carboxylesterase, arylesterase, lipase, phosphatase (mono- and diester), nuclease, nucleotidase, phytase, arylsulphatase 

2 amylase, cellulase, laminarinase, inulase, xylanase, dextranase, levanase, polygalacturonase, of-glucosidase, p-glucosidase, a-galactosidase, p-galactosidase, invertase 

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