A heterodimeric hyaluronate lyase secreted by the activated sludge bacterium Haliscomenobacter hydrossis

Haliscomenobacter hydrossis is a filamentous bacterium common in activated sludge. The bacterium was found to utilize hyaluronic acid, and hyaluronate lyase activity was detected in its culture. However, no hyaluronate lyase gene was found in the genome, suggesting the bacterium secretes a novel hyaluronate lyase. The purified enzyme exhibited two bands on SDS-PAGE and a single peak on gel filtration chromatography, suggesting a heterodimeric composition. N-terminal amino acid sequence and mass spectrometric analyses suggested that the subunits are molybdopterin-binding and [2Fe-2S]-binding subunits of a xanthine oxidase family protein. The presence of the cofactors was confirmed using spectrometric analysis. Oxidase activity was not detected, revealing that the enzyme is not an oxidase but a hyaluronate lyase. Nuclear magnetic resonance analysis of the enzymatic digest revealed that the enzyme breaks hyaluronic acid to 3-(4-deoxy-β-d-gluc-4-enuronosyl)-N-acetyl-d-glucosamine. As hyaluronate lyases (EC 4.2.2.1) are monomeric or trimeric, the enzyme is the first heterodimeric hyaluronate lyase.