[en] The protein and metal ion content in purified superoxid dismutase enzime (SOD) extracted from the alga Anacystis nidulans has been measured simultaneously using the ¹⁴N(d, p)¹⁵N nuclear reaction and the technique of proton induced X-ray spectroscopy. It has been shown that this enzime contains Fe ions. On the ground of the quantitative assessment of these two measurements, the molecular weight is calculated to be 38 000 +- 8000 dalton. The sensitivity of the method is very high: the bombarded material was about 0.4 picomole protein, it contained 2.2x10^-11 g Fe, and the measurement could be performed with even 100 times less material. (D.P.)