Preparation and Properties of β-Glucuronidase

Publisher Summary This chapter discusses the preparation and properties of β–glucuronidase. All mammalian tissues contain a group-specific enzyme that catalyzes the hydrolysis of the biosynthetic β-D-glucopyranosiduronic acids of all types to the aglycons and D-glucuronic acid. This enzyme is commonly known as “β-glucuronidase,” a term that will be employed in the following pages. In the same way, for the sake of brevity, β-D-glucopyranosiduronic acids will often be referred to as β-glucuronides. Enzymes that decompose β-glucuronides have been obtained from diverse sources other than the mammalian cell. β-Glucuronidase finds its major application at the present time as a reagent for the hydrolysis of urinary steroid D-glucuronides, for which purpose it has certain advantages over mineral acids, and the rapid changes in tissue β-glucuronidase activity induced in vivo by certain steroid and pituitary hormones offer possibilities for the rapid measurement of the hormones. The enzyme might perhaps be employed with advantage as a hydrolytic agent in carbohydrate chemistry. Most of the assay methods depend upon colorimetric determination of the amount of aglycon liberated from a specified concentration of substrate at a fixed pH, the results being read from a standard curve. Unit β-glucuronidase activity is then almost universally expressed as that which liberates 1 μg. of aglycon in 1 hr. at 38°; a similar type of unit is employed when the liberation of D-glucuronic acid is followed.