Glucosidases and galactosidases in soils

• Published in: Soil biology & biochemistry 1988, Vol.20 (5), p.601-606
• Main Authors: Eivazi, F., Tabatabai, M.A.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biochemistry and biology; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; Fundamental and applied biological sciences. Psychology; Organic matter; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Soil science
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/0038-0717(88)90141-1

An improved method to assay activities of α- and β-glucosidases and α- and β-galactosidases in soils is described. It involves extraction and colorimetric determination of the p-nitrophenol released when 1 g of soil is incubated with 5 ml of buffered p-nitrophenyl glycoside solution at 37°C for 1 h. The reagents [0.5 M CaCl 2 and 0.1 M Tris (hydroxymethyl)aminomethan THAM, pH 12] used for extraction of the p-nitrophenol released give quantitative recovery of p-nitrophenol added to soils and do not cause chemical hydrolysis of the substrates. Results showed that these enzymes have their optimum activities at buffer pH 6.0. The initial rates of p-nitrophenol release obeyed zero-order kinetics. β-Glucosidase activity was the most predominant of the four enzymes. The temperature dependence of the rate constant conformed to the Arrhenius equation up to the point of enzyme inactivation (60°C for α- and β-galactosidases and α-glucosidase and 70°C for β-glucosidase). The average activation energy values of these enzymes in three soils were 43.1, 30.8, 57.0 and 32.6 kJmol −1 for α-glucosidase, β-glucosidase, α-galactosidase and β-galactosidase activities, respectively. By using the Lineweaver-Burk plot. the K m values were the lowest for β-glucosidase activity. The V max values varied among the four enzymes and soils studied.