Deamidates glutamine residues on chemoreceptors (MCPs). CheD-mediated MCP deamidation is required for productive communication of the conformational signals of the chemoreceptors to the CheA kinase. In addition, demethylates methylated glutamate residues on chemoreceptors Mcp2 and Mcp4. Enhances the activity of CheC. H2O + L-glutaminyl-[protein] = L-glutamyl-[protein] + NH4(+) [protein]-L-glutamate 5-O-methyl ester + H2O = H(+) + L-glutamyl-[protein] + methanol Heterodimer with CheC. The CheC-CheD heterodimer interacts with phosphorylated CheY. Belongs to the CheD family.