Dimethyl sulfide (DMS) is a climate-active gas produced from dimethylsulfoniopropionate (DMSP) by DMSP lyases, one of which is DddQ. The relative importance of DddQ compared to other lyases is not yet fully understood, and its low activity was one reason for the claim that it might not be an authentic DMSP lyase [1]. Here we examined the kinetic parameters, metal ions, and structure of DddQ of the marine bacterium Ruegeria pomeroyi DSS-3. We determined that the relevant metal ions for this DddQ are Fe(II) and Mn(II). The specific activity of Fe(II)-DddQ was 17.8 1.6 mol mg-1 min-1 and that of Mn(II)-DddQ was 3.3 0.6 mol mg-1 min-1. Its activity level and relevant metal ions are comparable to those of DddW [2]. The crystal structure of this DddQ indicates a cupin-fold enzyme and high structural similarity to the DddQ of R. lacuscaerulensis. Based our findings, we conclude that DddQ is a bona fide DMSP lyase.