Enzymes are part of the protein family, and as substrate-specific catalysts will the rate of biochemical reactions and facilitate the breakdown of complex molecules.

you must remain stopped until the stop signal is retracted and the red lights are turned off. approaching traffic in the opposite roadway of a divided highway shall not be required to stop, even if the school bus has the stop-arm extended and the alternately flashing warning signal lamps on.

the answer is:

carbon dioxide