Homotaurine (3-aminopropanesulfonic acid) and sulfopropanoate (3-oxopropanesulfonic acid), its oxidative deamination product, are C3-organosulfonates that occur in marine algal metabolism, the human diet and microbial sulfur cycling. Here we report the identification and characterization of a complete bacterial pathway for catabolism of homotaurine via sulfopropanoate. The pathway involves three phases: import of homotaurine and conversion to sulfopropanoate through the known nitrogen assimilation pathway, transformation of sulfopropanoate to sulfolactate through a new pathway that bears close resemblance to steps in the citric acid cycle, and finally, biomineralization using a known pathway for sulfolactate breakdown. The core sulfopropanoate to sulfolactate module is widespread and emphasizes the important of this transformation as a key module in C3-(amino)organosulfonate breakdown.