Brookhaven biochemists have engineered an enzyme that increases output of alkanes, long carbon-chain molecules that could be a direct replacement for the hydrocarbons in gasoline.
Unlike the process of breaking down plant biomass to sugars and fermenting them to ethanol, biologically produced alkanes could be extracted and used directly as fuel. But to do that efficiently, an alkane-producing enzyme - called aldehyde-deformylating oxygenase, or ADO - would have to work continuously. And in early tests, it mysteriously stopped working after three to five “turnovers”, like a car engine sputtering out.
Biochemist John Shanklin and his team explored why the system was stalling and found that a by-product of the reaction was hydrogen peroxide, which was halting alkane production. So they introduced another enzyme, catalase, which feeds on hydrogen peroxide.
“When we added both enzymes, instead of the reaction turning over three times before stopping, it ran for more than 225 cycles,” Shanklin said.
They linked together these two enzymes into a dream team enzyme that does double duty. The ADO cranks out alkanes and the catalase eats up the hydrogen peroxide. The latter reaction also generates oxygen, which is needed for alkane production. So the combo enzyme not only takes care of the inhibiting by-product, it also spurs on the reaction.
The scientists are now working to install the dual enzyme in algae or green plants.