Abstract:
Molybdenum enzymes (Mo-enzymes) contain a molybdenum cofactor (MoCo) in the active site.
These enzymes are potentially interesting for studying the survival mechanism of fish under hypoxic water conditions. This is because Mo-enzymes can synthesize nitric oxide from nitrates
and nitrites, which are present in high concentrations under hypoxic water conditions. However,
there is currently no method for assessing the Mo-enzymes content in the fish internal organs.
Methods capable of determining Mo-enzymes content in the fish are of major importance. For
this purpose, a method for quantitative determination of MoCo from plant tissues was modified.
We demonstrated the Mo-enzyme content assessment by isolated MoCo from the fish’s internal
organs and the Neurospora crassa nit-1 extract containing inactive NADPH nitrate reductase. The
Mo enzyme content was calculated using a calibration curve in nM of nitrites as a product of
restored NADPH reductase activity after complementation with MoCo. Here we present a robust
laboratory method which can be used to assess the content of Mo-enzymes in the internal organs
of fish.
