Inhibition of Emulsin by D ‐Gluconhydroximo‐1,5‐lactone and Related Compounds

At pH 4.5 (citrate buffer), D ‐gluconhydroximo‐lactone ( 2 ), the N ‐methylurethane 3 and the N ‐phenylurethane 4 inhibit competitively the hydrolysis of p ‐nitrophenyl β‐ D ‐glucopyranoside by emulsin. The IC 50 values of 2, 3 , and 4 were 1.6 × 10 −4 , 1.0 × 10 −4 , and 5.8 × 10 −6 M , respectively. The K i values of 2 and 4 were 9.8 × 10 −5 and 2.3 × 10 −6 M , respectively, while D‐glucono‐1,5‐lactone ( 1 ) showed IC 50 = 1.1 × 10 −4 M and K i = 3.7 × 10 −5 M .