IBA propagation across the PANTHER proline-rich cell-wall protein group (PTN007993732) assigned "cytoplasm" to ENOD2; this is inconsistent with the protein's signal peptide and cell-wall protein class, which indicate secretion to the apoplast.

SwissProt keyword-derived (SPKW) annotation present in the Sept 2025 goa_uniprot_gcrp snapshot but removed from the current GOA release after GOA retired the keyword2GO pipeline for cellular organisms.

For ENOD2, the keyword "Nodulation" (UniProt KW line) mapped to GO:0009877 nodulation; this reflects the gene's nodule-specific EXPRESSION rather than a demonstrated mechanistic role, so its removal is an appropriate de-over-annotation.

309-aa secreted Precursor with an N-terminal signal peptide (SIGNAL 1..25) and a CHAIN (26..309) for the mature Early nodulin-75 protein.

The mature protein is largely disordered with multiple proline-rich compositional-bias segments; member of the nodulin 75 family and the InterPro "Proline-rich_CW_protein" family (IPR051308).

UniProt FUNCTION states "Involved in early stages of root nodule development" and INDUCTION "During nodulation in legume roots after Rhizobium infection"; evidence is at transcript level (PE 2).

Synthesises van de Wiel et al. 1990 (EMBO J, DOI 10.1002/j.1460-2075.1990.tb08073.x) and Foster 1998 (dissertation), concluding soybean ENOD2 is a secreted, proline-rich (hydroxyproline-rich) cell-wall protein precursor expressed early during nodulation.

In situ hybridisation localises ENOD2 mRNA predominantly to the nodule inner cortex / nodule parenchyma and to cells surrounding the connecting vascular bundle between nodule and root; ENOD2 is detectable ~day 6 and strong by ~day 10, before nitrogen fixation.

The protein is described as very proline-rich, built largely from pentapeptide repeats, strongly resembling soybean cell-wall glycoproteins, with a putative N-terminal signal peptide consistent with secretion to the apoplast/cell wall.

The proposed structural role in nodule-parenchyma morphology and possible oxygen-diffusion-barrier function is a hypothesis based on localisation plus protein class, not a demonstrated biochemical mechanism; a later review argues ENOD2 is unlikely to be solely responsible for oxygen regulation. ENOD2 is used mainly as a molecular marker of nodule-parenchyma differentiation and early nodule development.