A Model of Photoinhibition Related to mRNA Instability in Ethylene Production by a Recombinant Cyanobacterium

Photoinhibition mechanism is studied for ethylene production by a recombinant cyanobacterium. The kinetic pattern of the production is similar to that of substrate inhibition in enzyme reactions, whereas the photoinhibition is believed not to be substrate-related, but to originate from the enzyme for ethylene formation. In a proposed model, the inhibition is attributed to the process of enzyme synthesis, where light-dependent mRNA decomposition affects enzyme concentration. A mathematical formula derived accordingly for light dependence of ethylene production rate gives the same form as a well-known equation of substrate inhibition. The model also predicts ethylene production under dark condition, which has been observed experimentally.