Being small, shapeless and inert a gas molecule does not seem to be an enzyme's dream of a substrate. Nevertheless evolution has provided a host of enzymes which can interact specifically with gas molecules such as oxygen, carbon dioxide, nitrogen, hydrogen etc. Many of these enzymes play dominant roles on the world scene in biogeochemical cycles. On the cellular level they tend to be closely connected to the energy conserving apparatus. We define Gas Enzymology as the study of these enzymes. Historically, Gas Enzymology is a subspecialty of bioenergetics. Its foundations, technical as well...