Detection, quantification and characterization of β-glucosaminidase activity in soil

Abstract A simple and sensitive method was developed to detect and quantify N-acetyl-β- D -glucosaminidase (EC 3.2.1.30) activity in soil. This enzyme is also listed as β-hexosaminidase (EC 3.2.1.52) in Enzyme Nomenclature. The optimum pH and temperature for the enzyme were approximately pH 5.5 and 63°C, respectively. The Km and Vmax values were calculated from three linear transformations of the Michaelis–Menten equation. The Km values of the enzymatic reaction in the two soils tested ranged from 0.56 to 1.48 mM and the Vmax values ranged from 29 to 40 mg ρ-nitrophenol released kg−1soil h−1. The activation energy (Ea) for the enzymatic reaction was about 58 kJ mol−1 for soils tested. The Q10 values ranged from 1.35 to 2.50 at temperatures ranging from 10 to 60°C. With the exception of field-moist Renfrow soil, neither chloroform fumigation nor toluene pretreatment of soil samples affected the activity of β-glucosaminidase significantly. The activity of this enzyme in field-moist Renfrow soil increased about 20% upon fumigation or toluene treatment. Autoclaving the soils reduced β-glucosaminidase activity by about 58% in the air-dried soils and 96% in the field-moist soils. Air-drying of field-moist soil samples reduced β-glucosaminidase activity by 12% and 22% in Renfrow and Teller soil, respectively. Our results suggest that activity of β-glucosaminidase is mostly due to extracellular enzymes.