High throughput screening of enzyme activity with mass spectrometry imaging

Tristan de Rond, Megan Danielewicz, Trent Northen
2015 Current Opinion in Biotechnology  
Mass spectrometry imaging (MSI) has found a diversity of applications ranging from localizing metabolites and proteins in tissues to investigating microbial interactions, and as a result is perhaps the fastest growing subfield of mass spectrometry. Advances in surface mass spectrometry technologies are equally applicable to the analysis of arrayed samples. One promising field in which this capacity has been leveraged is the high-throughput analysis of enzyme activity, an important step in the
more » ... velopment of a wide range of biotechnologies. This review article describes several emerging approaches that seek to improve the quality and scope of this application of MSI. Graphical abstract Introduction Understanding enzymatic catalysis is at the heart of biochemistry and essential for biotechnologies from biocatalysis to drug development [1] [2] [3] [4] . Functional gene annotation of the overwhelming variety of enzymes identified in recent genomic efforts, combined with the diversity of possible substrates, inhibitors, and reaction conditions entails the exploration of a daunting experimental space. Classically, large-scale enzyme characterization efforts have employed surrogate substrates that change spectroscopic properties upon enzyme action. While high throughput (subsecond/sample), these approaches are applicable only to a narrow range of biochemical transformations, can be difficult to develop, have high false discovery rates, and are typically unable to distinguish multiple competing reactions. HPLC and LC-MS techniques have proven to be important compliments to spectrophotometric screens for many biological applications because of their analytical specificity and accuracy [5] . However, they are much lower throughput (minutes/sample) and are therefore typically © 2014. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ employed for smaller scale studies or hit-confirmation. Here we will focus on the application of Mass Spectrometry Imaging (MSI) towards high-throughput enzyme activity assays. MSI is perhaps the fastest growing subfield of mass spectrometry (MS), allowing for the mass analysis of thousands of distinct locations on a surface. While the primary application of MSI has been the localization of biomolecules within tissues[6], the technology likewise enables the comparison of thousands of spatially defined samples (for a discussion on sample deposition techniques, see Box 1). One emergent application of this capability is the highthroughput characterization of enzyme activity. A major challenge for any application of MSI is the limited number of analytes that can be detected simultaneously compared to the much more comprehensive -but low-throughput -analysis achieved by integrating chromatography with MS (e.g. GC-MS or LC-MS), which reduces the number of molecules competing for desorption and ionization at a given time. A variety of approaches have been developed to improve analyte detection in direct infusion methods. For example, the Agilent RapidFire platform automates a solid phase extraction step prior to analysis, in effect accomplishing HT-ESI-MS [7]. Recently, a similar but spatially defined extraction step has been developed for MSI [8] . Additionally, cleanup of samples on a surface can be achieved through selective analyte immobilization and washing off contaminants.
doi:10.1016/j.copbio.2014.07.008 pmid:25129648 fatcat:sptlpviud5hwneijzytroaqvbe