Involved in the maturation of [NiFe] hydrogenases. Along with HypF, it catalyzes the synthesis of the CN ligands of the active site iron of [NiFe]-hydrogenases. HypE catalyzes the ATP-dependent dehydration of the carboxamido group attached to its C-terminal cysteine to a cyano group (PubMed:12586941, PubMed:15291820). The cyano group is then transferred from HypE to the HypC-HypD complex or the HybG-HypD complex (PubMed:15504408). ATP + C-terminal S-carboxamide-L-cysteinyl-[HypE protein] = ADP + C-terminal S-cyanate-L-cysteinyl-[HypE protein] + H(+) + phosphate Protein modification; [NiFe] hydrogenase maturation. Homodimer (PubMed:18065529). Forms a complex with HypF (PubMed:15291820, PubMed:18065529). Also forms a complex with HypC, or HybG, and HypD (PubMed:15504408, PubMed:16412426). Modified by HypF, which adds a carboxamido group to the thiolate of the C-terminal cysteine, yielding a protein-S-carboxamide. The carboxamido group is then dehydrated by HypE itself to yield a protein-thiocyanate. Belongs to the HypE family.