Behaviour of the NO-β-d-glucosiduronic acid of N-acetyl-N-phenylhydroxylamine as a substrate for β-glucuronidase

Abstract

1. Biosynthetic sodium (N-acetyl-N-phenylhydroxylamine NO-beta-d-glucosid)-uronate is hydrolysed completely by purified mouse urinary beta-glucuronidase into the products N-acetyl-N-phenylhydroxylamine and glucuronic acid. The hydrolysis is inhibited by saccharo-(1-->4)-lactone. These results not only confirm the identity and purity of the substrate but also establish it as a substrate for beta-glucuronidase. 2. Mammalian and bacterial beta-glucuronidase preparations hydrolysed the substrate at a rate one-fifth of that for (phenolphthalein beta-d-glucosid)uronic acid under the optimum conditions of hydrolysis for each source. 3. The pH optimum is 4.1 and the Michaelis constant, K(m), is 3.3x10(-4)m with purified mouse urinary beta-glucuronidase as the enzyme source acting on the NO-beta-d-glucosiduronic acid. The aglycone after extraction into chloroform was quantitatively determined spectrophotometrically at its absorption maximum (256mmu). 4. The hydrolysis was studied as a function of time and temperature. 5. From a consideration of the chemical and enzymic properties of this NO-beta-d-glucosiduronic acid it is possible to suggest its catabolism in vivo.