Cloning and expression of the dimethylsulfoniopropionate lyase gene dddY and the identification of the key amino acids necessary for its activity

The abundant solute dimethylsulfoniopropionate (DMSP) is crucial in marine ecosystems. In this study, a bacterium, Acinetobacter sp. ZS25, capable of completely mineralizing DMSP and producing DMS and acrylate, was isolated. The possible DMSP degradation pathway was primarily identified. The role of DMSP lyases DddY was identified through a combination of genomic comparison, gene knockout and heterologous expression. The K_m and k_cat of AsDddY for DMSP were 2.6 mM and 12.7 × 10³ s⁻¹, respectively. Site-directed mutagenesis was employed to examine the influence of specific amino acid residues (Thr131, Asp181, Tyr225, Gly230, Gly250, His263, His265, Glu269, Tyr271, Leu274, Tyr331, and His338) within AsDddY, elucidating their critical roles in the protein's functionality. Bioinformatics analysis revealed 19 distinct acu-dddY cluster order types, while the number of strains with a complete dddY-acu cluster is limited. Our findings offer novel insights into the mechanisms underlying DMSP biodegradation and enhance our understanding of the diversity of acu-dddY clusters present in natural bacterial populations.