Methods, compositions, kits, and apparatus are provided wherein the aminoacyl-tRNA synthetase 
system is used to analyze amino acids. The method allows very small devices for quantitative or semi-quantitative analysis of the amino acids in samples or in sequential or complete proteolytic digestions. The methods can be readily applied to the detection and / or quantitation of one or more 
primary amino acids by using cognate aminoacyl-tRNA synthetase and cognate tRNA. The basis of the method is that each of the 20 synthetases and / or a tRNA specific for a different 
amino acid is separated spatially or differentially labeled. The reactions catalyzed by all 20 synthetases may be monitored simultaneously, or nearly simultaneously, or in parallel. Each separately positioned synthetase or tRNA will 
signal its cognate 
amino acid. The synthetase reactions can be monitored using continuous spectroscopic assays. Alternatively, since 
elongation factor Tu:GTP (EF-Tu:GTP) specifically binds all AA-tRNAs, the 
aminoacylation reactions catalyzed by the synthetases can be monitored using ligand assays. Microarrays and microsensors for 
amino acid analysis are provided. Additionally, 
amino acid analysis devices are integrated with 
protease digestions to produce miniaturized enzymatic sequenators capable of generating either N- or C-terminal sequence and composition data for a 
protein or 
peptide. The possibility of 
parallel processing of many samples in an automated manner is discussed.