Deamidates 'Gln-593' and 'Gln-594' of the chemoreceptor McpA. In addition, deamidates other chemoreceptors, including McpB and McpC. CheD-mediated MCP (methyl-accepting chemotaxis proteins) deamidation is required for productive communication of the conformational signals of the chemoreceptors to the CheA kinase. CheD is absolutely required for a behavioral response mediated by McpC but is not required for the response to asparagine mediated by McpB. CheD is necessary for the generation of wild-type prestimulus CheA autophosphorylation levels. Also required for methylation of MCPs by CheR. In addition, enhances the activity of CheC 5-fold in vitro. H2O + L-glutaminyl-[protein] = L-glutamyl-[protein] + NH4(+) Forms a complex with CheC. Cells exhibit poorly methylated receptors, are tumbly and have a decreased sensitivity to attractants. Belongs to the CheD family.