Involved in the biosynthesis of the siderophore pyochelin (PubMed:9846750, PubMed:11208777). Adenylates L-cysteine and loads it onto its peptidyl carrier domain via a thioester linkage to the phosphopanthetheine moiety (By similarity). Then forms a peptide bond between the salicyl-thiazolinyl intermediate bound to the second carrier domain of PchE and the cysteine bound to its own peptidyl carrier domain to form the salicyl-thiazolinyl-cysteinyl-S-PCP2 intermediate. It subsequently cyclizes the C-terminal cysteine to form the second thiazoline heterocycle in the salicyl-thiazolinyl-thiazolinyl-S-PCP2 intermediate (By similarity). When this intermediate is released by the action of a thioesterase, it produces the tricyclic acid hydroxyphenyl-thiazolyl-thiazolinyl-carboxylic acid (HPTT-COOH), an advanced intermediate containing the aryl-4,2-bis-heterocyclic skeleton of the bithiazoline class of siderophores (By similarity). ATP + holo-[peptidyl-carrier protein] + L-cysteine = AMP + diphosphate + L-cysteinyl-[peptidyl-carrier protein] Siderophore biosynthesis. Expression of the pchEF operon is strictly dependent on the PchR regulator and is induced by extracellular pyochelin, the end product of the pathway. Repressed by Fur and iron. Modular protein that contains a condensation/cyclization domain involved in the cyclization of the cysteine, an adenylation domain which activates the cysteine residue into an aminoacyl-AMP ester, a peptidyl carrier protein (PCP2) domain which bears a phosphopantetheinyl arm to attach the activated cysteine and a thioesterase domain (TE) that may release the newly synthesized peptide from the enzyme. Mutant can still form salicylate and Dha, but is no longer able to synthesize pyochelin. Belongs to the NRP synthetase family.