Abstract:
Acetylene is a slow-binding inhibitor of the Ni- and Fe-containing dimeric hydrogenase isolated
from Azotobacter vinelandii. Acetylene was released from hydrogenase during the recovery from inhibition.
This indicates that no transformation of acetylene to another compound occurred as a result of the interaction
with hydrogenase. However, the release of C2H2 proceeds more rapidly than the recovery of activity, which
indicates that release of C2H2 is not sufficient for recovery of activity. Acetylene binds tightly to native
hydrogenase; hydrogenase and radioactivity cuelute from a gel permeation column following inhibition with
14C2H2A. cetylene, or a derivative, remains bound to the large 65 000 MW subunit (and not to the small
35 000 MW subunit) of hydrogenase following denaturation as evidenced by SDS-PAGE and fluorography
of l4C2H,-inhibited hydrogenase. This result suggests that C2H2, and by analogy H,, binds to and is activated
by the large subunit of this dimeric hydrogenase. Radioactivity is lost from 14C2H,-inhibited protein during
recovery. The inhibition is remarkably specific for C2H2: propyne, butyne, and ethylene are not inhibitors.
