Inhibition of beta-N-acetylglucosaminidase by glycon-related analogues of the substrate.

Inhibition studies on beta-N-acetylglucosaminidase (EC 3.2.1.30) of widely differing origins (animal, plant, fungus) were carried out with N-acetylglucosaminono-1,5-lactone (1), N-acetylglucosaminono-1,5-lactam (2), 1,5-imino-N-acetylglucosaminitol (3), and N-acetylglucosaminono-1,5-lactone oxime (4). The inhibition was competitive in all cases, and Ki values were generally in the range of 0.15-2 microM, except for the fungal enzyme (5-20 microM). To assess the kinetics of enzyme-inhibitor complex formation, continuous enzyme activity monitoring was done with 3,4-dinitrophenyl-beta-N-acetylglucosaminide as the substrate. A slow approach to the binding-equilibrium in the time scale of minutes could not be observed with any of the inhibitors tested (1-4). The results are evaluated as to the bearing of the enzyme source on best performance of the test compounds, the sub-type of inhibition mechanism is discussed, and suggestions are made for further analogue syntheses as well as potential applications of 1-4 (particularly the O-phenylcarbamoyl derivative of the latter) in biological and medical research.

N-acetylglucosaminono-1,5-lactone oxime and the corresponding (phenylcarbamoyl)oxime. Novel and potent inhibitors of beta-N-acetylglucosaminidase.

Using N-acetylglucosaminono-1,5-lactone (1) as the reference, the inhibitory activity of its (formal) derivatives N-acetylglucosaminono-1,5-lactone oxime (2) and N-acetylglucosaminono-1,5-lactone O-(phenylcarbamoyl)-oxime (3) was tested against beta-N-acetylglucosaminidase of different origins (animal, plant, fungus). Displaying inhibition constants of 0.45 microM and 0.62 microM, for the animal and plant enzyme, respectively, the simple oxime 2 was about equally potent as the parent lactone 1, and 50-400 times more efficient than two recently described new beta-N-acetylglucosaminidase inhibitors. The (phenylcarbamoyl)oxime 3 performed even better, particularly with the fungal enzyme (Ki = 40 nM), i.e. was about 350 times more potent than the lactone. In all cases competitive inhibition was observed with 4-nitrophenyl-beta-N-acetylglucosaminide as the substrate. With Ki/Km ratios up to 3300 for 2 and 13,600 for 3, the mode of action of these novel inhibitors is probably that of transition state mimicry. Suggestions are made for their use as a tool in biological research.