entE (E. coli K-12, P10378, b0594) notes

Provenance of this review

• 2026-10-19: just deep-research ECOLI entE --provider falcon failed twice with
  Exception: Failed to authenticate (Edison API). No deep-research file exists; the
  review is grounded in the UniProt record (entE-uniprot.txt), GOA (entE-goa.tsv),
  and the cached primary literature in publications/. Most cached papers are
  abstract-only; PMID:19852513, PMID:20359185, PMID:20845982, PMID:18304323 and
  PMID:24561554 have full text.
• Also reviewed: NCBI PGAP output for WP_000026812.1 (entE-pgap-predictions-review.yaml).

Identity and family

• EntE is the stand-alone adenylation (A) enzyme of the enterobactin NRPS; UniProt:
  "Belongs to the ATP-dependent AMP-binding enzyme family" (ANL superfamily; PANTHER
  PTHR43767). Aryl acid adenylating enzyme (AAAE) class
  PMID:20359185.

Catalytic activity (core)

• Two half-reactions: DHB + ATP -> DHB-AMP + PPi, then DHB transfer onto the
  phosphopantetheine arm of holo-EntB ArCP domain
  PMID:20359185.
• First purification/characterisation, enzyme-bound DHB-adenylate
  PMID:2531000.
• EntB identified as the ArCP acylated by EntE
  PMID:9214294.
• Overall reaction GO:0008668 / EC 6.2.1.71 / RHEA:61652 is therefore exactly EntE's activity.
• Kinetics: Km DHB ~2.5-2.9 uM, Km holo-EntB 0.4-2.9 uM, Km ATP 0.43-1.2 mM (UniProt
  BIOPHYSICOCHEMICAL PROPERTIES, from PMID:20359185, PMID:2531000, PMID:9214294).
• Inhibited by bisubstrate analogues Sal-AMS and DHB-AMS (PMID:20359185).
• Side reaction: in absence of holo-EntB, DHB-AMP reacts with ATP giving Ap4A
  PMID:19852513.
  This is an in-vitro side activity; physiological relevance unproven.
• MbtH-like YbdZ copurifies with/affects EntF A-domain; EntE was purified alongside as
  comparison PMID:20845982.

What EntE does NOT do

• The DHB-serine amide bonds (and the ester bonds) are made by EntF, not EntE
  PMID:9485415.
  Hence GO:0047527 (2,3-dihydroxybenzoate-serine ligase activity; product N-(2,3-dihydroxybenzoyl)-L-serine)
  and EC 6.3.2.14 (whole enterobactin synthase reaction) describe the multi-protein
  synthetase; EntE contributes the first step only. UniProt nonetheless lists EC 6.3.2.14 on EntE.
• No CoA-ligase activity reported; the thiol acceptor is the phosphopantetheine of holo-EntB
  ArCP (or D-pantetheine as a poor surrogate, Km 34.2 mM, UniProt from PMID:20359185).

Partners

• EntB: DHB binding to EntE promotes EntE-EntB complexation
  PMID:19699210.
• EntA: tetrameric EntA binds EntE and stimulates activity 6-fold
  PMID:21166461.
• No stable synthetase complex in vitro PMID:9485415.

Location

• Cytosolic proteomics (PMID:18304323). Small fraction membrane-associated
  PMID:10692387.

Genetics / process

• entE mutants cannot convert DHB to enterochelin PMID:4939766.
• Iron-starvation induced, Fur-regulated (UniProt INDUCTION).

PGAP

• WP_000026812.1 named by BlastRule NBR012093 (no GO); EC 2.5.1.-, 6.2.1.71, 6.3.2.14.
  Equivalog HMMs NF008192 and TIGR02275 (same product name) carry GO:0008668 and GO:0019290 but
  are not the naming model, so PGAP emits no GO. See predictions review.
• EC 2.5.1.- (alkyl/aryl transferases) is a misclassification: DHB transfer to the
  phosphopantetheine thiol is an aroyl (acyl) transfer and is the second half of EC 6.2.1.71.