Stability of ribonuclease A under hydrothermal conditions in relation to the origin-of-life hypothesis: verification with the hydrothermal micro-flow reactor system

Abstract

The stability of ribonuclease A (RNase A) was quantitatively investigated with the hydrothermal micro-flow reactor system (HFRS) at temperatures of up to 275 °C from the viewpoint of the hydrothermal origin-of-life hypothesis. The enzymatic activity of RNase A was studied with regard to the catalytic degradation of polynucleotides with anion-exchange high-performance liquid chromatography, while the degradation of RNase A to shorter molecules was analyzed by size exclusion chromatography (SEC) and mass spectrometry (MS). The degradation of RNase A started within 10 s at 200 °C, and the enzymatic activity disappeared almost completely after 25 s. SEC and MS analyses indicated that RNase A was thermally degraded to 2 large fragments, which, along with RNase A, were further decomposed to smaller fragments. This study showed that RNase A is fairly stable under normal conditions, but its enzymatic activity disappears rapidly at extremely high temperatures. The half life of RNase A and its fragments under hydrothermal conditions is comparable to or longer than the enzymatic reaction time scale of modern enzymes. Furthermore, this study demonstrates that HFRS is reliable and useful for verifying the stability of several proteins in fundamental and applied research as well as for studying the origin-of-life problem.