Kinetic analysis questions chemistry proposed for the origin of life

Kinetic and thermodynamic considerations reported by researchers at the Tokyo Institute of Technology suggest that thioesters at the heart of many theories on the origin of life are unlikely primordial contributors.

How life emerged from a primordial soup of simple chemicals remains unknown. However scientists have proposed several possible schemes for the origin of life, many of which rely on chemistry involving thioesters such as thioacetic acid (TAA) and methylathioacetate (MTA). Now results of kinetic and thermodynamic considerations reported by Kuhan Chandru and his colleagues at the Tokyo Institute of Technology, question the likelihood of these schemes.

Many of the reactions that form biological matter require enzymes that would not have existed in prebiotic times. However, the high temperatures in hydrothermal vents can overcome reaction barriers without the need for enzymes, making them widely considered likely sites for the origin of life. With this in mind, Chandru along with colleagues led by Jim Cleaves - a researcher affiliated with Tokyo Institute of Technology in Japan and the Institute for Advanced Study in Princeton, - studied the reaction kinetics in the conditions found in hydrothermal vents.

The researchers used nuclear magnetic resonance (NMR) to study the reversible hydrolysis of TAA and MTA in a range of possible pH, temperature and concentration conditions common to hydrothermal settings. They conclude that "TAA and MTA differ significantly in terms of their stability and reactivity as a function of pH and temperature, though both are implausible prebiotic reagents for different reasons in different contexts."

The researchers also add that the results suggest "estimates of the ubiquity of suitable environments for the origin of life in and beyond our solar system may be somewhat overestimated, if these compounds are indeed crucial for jumpstarting early metabolism."

Source: Tokyo Institute of Technology