Reversible inhibitors of .beta.-glucosidase

Abstract

A variety of reversible inhibitors of sweet almond beta-glucosidase were examined. These included simple sugars and sugar derivatives, amines and phenols. With respect to the sugar inhibitors and, indeed, the various glycoside substrates, the enzyme has what can be considered a "relaxed specificity". No single substituent on glucose, for example, is essential for binding. Replacement of a hydroxyl group with an anionic substituent reduces the affinity while substitution with a cationic (amine) substituent enhances the affinity. Amines, in general, are good inhibitors, binding more tightly than the corresponding alcohols: pKiRNH3+ = 0.645pKiROH + 1.77 (n = 9, r = 0.97). The affinity of a series of 10 primary amines was found to be strongly influenced by substituent hydrophobicity: pKi = 0.52 pi + 1.32 (r = 0.95). The major binding determinant of the glycoside substrates is the aglycon moiety. Thus, the Ki values of phenols are similar in magnitude to the Ks values of the corresponding aryl beta-glucoside. The pH dependence for the inhibition by various phenols indicates that it is the un-ionized phenol which binds to the enzyme when an enzymic group of pKa = 6.8 (+/- 0.1) is protonated. The affinity of the phenol inhibitor is dependent on its basicity with a Brønsted coefficient for binding of beta = -0.26 (n = 14, r = 0.98). The pH dependence of the binding of two particularly potent beta-glucosidase inhibitors was also examined. 1-Deoxynojirimycin (1,5-dideoxy-1,5-imino-D-glucitol) has a pH-corrected Ki = 6.5 microM, and D-glucono-1,5-lactam has a pH-corrected Ki = 29 microM.(ABSTRACT TRUNCATED AT 250 WORDS)

Origin of oxidized cellulose degradation products and mechanism of their promotion of cellobiohydrolase I biosynthesis in Trichoderma reesei

“…No significant differences in this respect were observed between the two enzymes. The data described in this study confirm earlier studies of this enzyme from other organisms (Dale et al, 1985). CBL produces a characteristic competitive type of inhibition of cellobiose hydrolysis with a corresponding Ki of 27 f 6 p~.…”

A glycosidase antibody elicited against a chair-like transition state analog by in vitro immunization

“…In particular, ␦-gluconolactone, an inhibitor of lysozyme (K i ϭ 200 M), and ␦-gluconolactam, an inhibitor of sweet almond ␤-glucosidase B (K i ϭ 29 M), resemble the half-chair conformation but lack a positive charge (30,31). The cyclic amine inhibitors including 1-deoxynojirimycin (K i ϭ 18 M for sweet almond ␤-glucosidase), castanospermine, and australine rely on charge complementarity between the protonated nitrogen and negatively charged active-site carboxylates (20,21).…”

“…The cyclic amine inhibitors including 1-deoxynojirimycin (K i ϭ 18 M for sweet almond ␤-glucosidase), castanospermine, and australine rely on charge complementarity between the protonated nitrogen and negatively charged active-site carboxylates (20,21). However, evidence suggesting that the nonprotonated species may be the true inhibitory agents casts some uncertainty on the precise mechanism of inhibition (30). The cyclic amidines (32), which combine the half-chair conformation and positive charge, inhibit ␤-glucosidase with a K i of roughly 10 M. The short lifetimes of the latter at physiological pH preclude their use as haptens to elicit catalytic antibodies (ref.…”

Calystegins of Physalts alkekengi var. Francheti (Solanaceae). Structure Determination and their Glycosidase Inhibitory Activities

“…7 A [19]. Dale et al [20] have examined the affinities of various sugar analogues for almond j3-glucosidase and have reported that the sugar analogues with the higher affinity for the enzyme have the hydroxyl groups at C2 and C3 diequatorial in their most stable conformation. It is interesting to note that removal of the hydroxyl group at C2 in glucose slightly reduces the affinity, suggesting a favorable interaction between the hydroxyl group at C2 and the enzyme.…”