Atmospheric CO₂ captured by biogenic polyamines is transferred as a possible substrate to Rubisco for the...

Biogenic polyamines are involved in a wide range of plant cellular processes, including cell division, morphogenesis and stress responses. However, the exact roles of biogenic polyamines are not well understood. We recently reported that biogenic polyamines that have multiple amino groups can react with CO₂ and accelerate calcium carbonate formation in seawater. The ability of biogenic polyamines to capture atmospheric CO₂ prompted us to examine their roles in photosynthesis. Here, we demonstrated that atmospheric CO₂ captured by biogenic polyamines is a candidate substrate for the carboxylation reaction of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), which is an enzyme involved in the first major step of carbon fixation during photosynthesis, and that biogenic polyamines can accelerate the carboxylation reaction of this enzyme because of their specific affinity for CO₂. Moreover, the results of our nuclear magnetic resonance (NMR) analysis showed that putrescine, which is the most common biogenic polyamine, reacts with atmospheric CO₂ and promotes the formation of carbamate derivatives and bicarbonate in aqueous environments. A sufficient amount of CO₂ is well known to be produced by carbonic anhydrase from bicarbonate in vivo. The present study indicates that CO₂ would be also produced by the equilibrium reaction from carbonate produced by biogenic polyamines and would be used as a substrate of Rubisco, too. Our results may suggest a new photosynthetic research strategy that involves CO₂-concentrating mechanisms and also possibly constitutes a potential tool for reducing atmospheric CO₂ levels and, consequently, global warming.