Enzymatic Pathways for the Consumption of Carbonyl Sulphide (COS) by Higher Plants*

Carbonyl sulphide (COS) is an important trace gas of the atmosphere. Considerable uncertainties remain concerning the global sinks of COS. Vegetation is believed to be an unqualified sink in the global cycle of COS. We investigated whether there is an enzymological background for the consumption of COS by higher plants in analogy to CO 2 . Photometric measurements demonstrated that all enzymes involved in C0 2 assimilation by higher plants can also metabolise COS. The key enzyme for COS metabolism in higher plants is carbonic anhydrase, an enzyme which probably directly splits COS into C0 2 and H 2 S. Such a pathway would explain the observed deposition of COS to vegetation.