A High‐Throughput Mass‐Spectrometry‐Based Assay for Identifying the Biochemical Functions of Putative Glycosidases

The most commonly employed glycosidase assays rely on bulky ultraviolet or fluorescent tags at the anomeric position in potential carbohydrate substrates, thereby limiting the utility of these assays for broad substrate characterization. Here we report a qualitative mass spectrometry–based glycosidase assay amenable to high‐throughput screening for the identification of the biochemical functions of putative glycosidases. The assay utilizes a library of methyl glycosides and is demonstrated on a high‐throughput robotic liquid handling system for enzyme substrate screening. Identification of glycosidase biochemical function is achieved through the observation of an appropriate decrease in mass between a potential sugar substrate and its corresponding product by electrospray ionization mass spectrometry (ESI‐MS). In addition to screening known glycosidases, the assay was demonstrated to characterize the biochemical function and enzyme substrate competency of the recombinantly expressed product of a putative glycosidase gene from the thermophilic bacterium Thermus thermophilus.     

Position‐Specific Mass Shift Analysis: A Systematic Method for Investigating the EI‐MS Fragmentation Mechanism of epi‐Isozizaene

The EI‐MS fragmentation mechanism of the bacterial sesquiterpene epi‐isozizaene was investigated through enzymatic conversion of all 15 synthetic (¹³C₁)FPP isotopomers with the epi‐isozizaene synthase from Streptomyces albus and GC‐MS and GC‐QTOF analysis including MS‐MS. A systematic method, which we wish to call position‐specific mass shift analysis, for the identification of the full set of fragmentation reactions was developed.     

A Combined High‐Resolution Mass Spectrometric and in silico Approach for the Characterisation of Small Ligands of β2‐Microglobulin

β₂‐Microglobulin (β₂‐m) is a protein responsible for a severe complication of long‐term hemodialysis, known as dialysis‐related amyloidosis, in which initial β₂‐m misfolding leads to amyloid fibril deposition, mainly in the skeletal tissue. Whereas much attention is paid to understanding the complex mechanism of amyloid formation, the evaluation of small molecules that may bind β₂‐m and possibly inhibit the aggregation process is still largely unexplored mainly because the protein lacks a specific active site. Based on our previous findings, we selected a pilot set of sulfonated molecules that are known to either bind or not to the protein, including binders that are anti‐amyloidogenic. We show how a complementary approach, using high‐resolution mass spectrometry and in silico studies, can offer rapid and precise information on affinity, as well as insight into the structural requisites that favour or disfavour the inhibitory activity. Overall, this approach can be used for predictive purposes and for a rapid screening of fibrillogenesis inhibitors.