A continuous spectrophotometric assay for Escherichia coli alanyl-transfer RNA synthetase

A new continuous spectrophotometric assay is demonstrated for Escherichia coli alanyl-tRNA synthetase. It involves beta-gamma adenylyl imidophosphate as a substitute for ATP in the pyrophosphate exchange reaction. The net conversion of beta-gamma adenylyl imidophosphate to ATP can be linked to NADP reduction by hexokinase and glucose-6-P dehydrogenase catalyzed reactions, which can be monitored at 340 nm. This assay can be extended to other aminoacyl-tRNA synthetases which can use beta-gamma nonhydrolyzable analogs of ATP as an ATP substitute.