Mechanism-based inhibition of GH127/146 cysteine glycosidases by stereospecifically functionalized L-arabinofuranosides

To understand the precise mechanism of the glycoside hydrolase (GH) family 127, a cysteine beta-L-arabinofur-anosidase (Arafase) - HypBA1 - has been isolated from Bifidobacterium longum in the human Gut microbiota, and the design and synthesis of the mechanism-based inhibitors such as L-Araf-haloacetamides have been carried out. The alpha-L-Araf-azide derivative was used as the monoglycosylamine equivalent to afford the L-Araf-chlor-oacetamides (alpha/beta-1-Cl) as well as bromoacetamides (alpha/beta-1-Br) in highly stereoselective manner through Stau-dinger reaction followed by amide formation with/without anomerization. Against HypBA1, the probes 1, especially in the case of alpha/beta-1-Br inhibited the hydrolysis. Conformational implications of these observations are discussed in this manuscript. Additional examinations using L-Araf-azides (alpha/beta-5) resulted in further mechanistic observations of the GH127/146 cysteine glycosidases, including the hydrolysis of beta-5 as the substrate and oxidative inhibition by alpha-5 using the GH127 homologue.

Automated summary

In this study, a cysteine beta-L-arabinofuranosidase (Arafase) called HypBA1 was isolated from Bifidobacterium longum in the human gut microbiota to investigate the mechanism of the glycoside hydrolase (GH) family 127. Moreover, design and synthesis of mechanism-based inhibitors, such as L-Araf-haloacetamides, were carried out. The experimental results showed that the probes 1, especially alpha/beta-1-Br, inhibited the hydrolysis of HypBA1. The conformational implications of these observations were also discussed. Further examinations using L-Araf-azides (alpha/beta-5) provided additional mechanistic observations of the GH127/146 cysteine glycosidases.