Transcriptional regulator required for the aerobic growth on D-malate as the sole carbon source. Induces the expression of dmlA in response to D-malate or L- or meso-tartrate. Negatively regulates its own expression. Expression of dmlR is subject to negative autoregulation under both aerobic and anaerobic growth conditions. Its level of expression is generally lower under anaerobic conditions than that under aerobic conditions. Deletion of dmlR inhibits aerobic growth on D-malate and inhibits the induction of dmlA expression by D-malate and L- and meso-tartrate. Belongs to the LysR transcriptional regulatory family.