Layer-by-layer self-assembly of sulfite oxidase and cytochrome c was carried out without additional polymeric polyelectrolytes. The arrangement shows a linear increase in the immobilized protein mass after each deposition cycle. The modified electrodes demonstrate electrocatalytic activity for sulfite oxidation generating catalytic current with a linear increase with the number of layers. This effect shows that, in the protein assembly without a polyelectrolyte, electron transfer occurs, thus supporting the concept for direct interprotein electron exchange.