| Evidence type | Key findings (function, EC, substrates) | Domain architecture | Quantitative data | Localization inference | Source (citation id, year, URL) |
|---|---|---|---|---|---|
| Biochemical | **Fae1A is a feruloyl esterase, not a cellulase**; hydrolyzes feruloyl-polysaccharides and small hydroxycinnamate esters; paper explicitly identifies **EC 3.1.1.73** and tests ethyl ferulate, methyl ferulate, methyl caffeate, methyl *p*-coumarate, methyl sinapate, plus insoluble wheat arabinoxylan (pqac-00000005, pqac-00000007) | N-terminal **signal peptide** + **CE1** catalytic module + **CBM6** + **dockerin**; 489 aa, estimated 53.1 kDa (pqac-00000005, pqac-00000007) | Specific activities (U/μmol protein): EFA **15.7 ± 1.6** (full-length) vs **20.7 ± 1.9** (CE1 only); MFA **26.6 ± 0.78** vs **37.9 ± 2.7**; MCA **9.8 ± 0.73** vs **18.0 ± 2.3**; MpCA **13.4 ± 0.98** vs **12.9 ± 1.5**; MSA **18.1 ± 0.63** vs **29.5 ± 1.7**; insoluble wheat arabinoxylan **2.20 ± 0.26** vs **1.33 ± 0.15** (pqac-00000007) | Signal peptide supports **secretion**; dockerin supports **cellulosome incorporation** by cohesin–dockerin interaction; function is de-esterification of hemicellulose/plant cell wall crosslinks rather than cellulose hydrolysis (pqac-00000012, pqac-00000013) | (pqac-00000005, pqac-00000007, pqac-00000012, pqac-00000013), 2020, https://doi.org/10.1016/j.enzmictec.2020.109546 |
| Biochemical | **CBM6 enhances activity on native insoluble arabinoxylan** but not on small soluble esters; authors conclude CBM6 is important for releasing ferulic acid from native substrate (pqac-00000005, pqac-00000009, pqac-00000010) | Same architecture; truncation comparison between full-length Fae1A and CE1-only construct isolates CBM6 contribution (pqac-00000006, pqac-00000007) | Time course: CBM6 advantage visible through **1–2 h** on insoluble wheat arabinoxylan; by **6 h** CE1-only catches up, consistent with localized early action at nonreducing ends (pqac-00000007, pqac-00000010) | Supports an **extracellular/cellulosomal accessory hemicellulose-debranching role**, improving early access to feruloylated arabinoxylan regions (pqac-00000010, pqac-00000012) | (pqac-00000005, pqac-00000007, pqac-00000009, pqac-00000010, pqac-00000012), 2020, https://doi.org/10.1016/j.enzmictec.2020.109546 |
| Biochemical | **CBM6 binds xylan-related ligands**, not arabinose ligands or ferulic acid; authors infer recognition of **nonreducing-end xylopyranosyl residues**, with notable affinity for arabinoxylo-oligosaccharide **A2XX** (pqac-00000008, pqac-00000009, pqac-00000010) | Isolated **CBM6** tested separately; sequence most similar to CBM6a-like proteins (69% identity to a characterized CBM6a-1 protein) (pqac-00000006) | ITC Ka (×10^3 M^-1): xylose **14.0 ± 1.0**, xylobiose **32.0 ± 2.7**, xylotriose **18.5 ± 4.1**, xylohexaose **26.6 ± 2.1**, pNP-Xp **24.2 ± 4.7**, A2XX **18.9 ± 1.0**; no binding to arabinobiose, pNP-Af, arabinooligosaccharides tested, or ferulic acid. Fluorometric Kd: xylobiose **114 ± 1.0 μM**, A2XX **60.1 ± 0.9 μM**; competitive binding to same site (pqac-00000008, pqac-00000009) | CBM6 substrate targeting is consistent with **extracellular docking onto arabinoxylan/xylan surfaces** before CE1-catalyzed ester removal (pqac-00000008, pqac-00000010) | (pqac-00000006, pqac-00000008, pqac-00000009, pqac-00000010), 2020, https://doi.org/10.1016/j.enzmictec.2020.109546 |
| Biochemical / pathway context | Authors state **R. josui produces a cellulosome** and describe it as a scaffoldin with CBM and repeated cohesins recruiting catalytic subunits through dockerins; several **hemicellulases** for arabinoxylan/arabinan degradation have been identified as cellulosomal components (pqac-00000005, pqac-00000012) | Fae1A architecture fits this logic: secreted enzyme with **dockerin** and substrate-targeting **CBM6** (pqac-00000005, pqac-00000012) | No direct in vivo stoichiometry for Fae1A reported in the available excerpts | Strong inference that Fae1A is a **secreted, potentially cellulosome-associated hemicellulose-active accessory enzyme** acting in plant biomass degradation (pqac-00000012, pqac-00000013) | (pqac-00000005, pqac-00000012, pqac-00000013), 2020, https://doi.org/10.1016/j.enzmictec.2020.109546 |
| Genomics / review | Comparative genomics of **Ruminiclostridium-type** species places **R. josui JCM 17888** among simple-cellulosome producers; species carry a **cip-cel operon** and some possess a **xyl-doc cluster** for secreted dockerin-bearing hemicellulases (pqac-00000011) | Across 576 dockerin-bearing catalytic subunits, major architectures include **CD-Doc**, **CD-CBM-Doc**, **Doc-CD**; dockerins linked with **CBM6 + GH10/26/30/43** are associated mainly with **hemicellulose degradation**, supporting the functional context of CBM6-dockerin enzymes in this genus (pqac-00000011) | Statistics: **576** dockerin-bearing catalytic subunits analyzed; dockerin location **76.9% C-terminal**, **18.1% N-terminal**, **5.0% middle**; architecture counts included **250 CD-Doc**, **135 CD-CBM-Doc**, **98 Doc-CD**; cip-cel operons contain **10–16 genes** after scaffoldin; cohesin counts per scaffoldin about **2–14** (pqac-00000011) | Supports classification of Fae1A-like proteins as **extracellular dockerin-bearing biomass-degrading enzymes**, likely positioned within the hemicellulose arm of simple cellulosomes (pqac-00000011) | (pqac-00000011), 2023, https://doi.org/10.3389/fmicb.2023.1288286 |
| Review | General expert review: cellulosomes are **extracellular multienzyme complexes** assembled via **cohesin–dockerin** interactions, often containing cellulases, hemicellulases, and pectinases; review includes **Clostridium/Ruminiclostridium josui** among producers (pqac-00000014) | Not Fae1A-specific, but fully consistent with signal peptide + dockerin architecture and a hemicellulose-active accessory function | No Fae1A-specific kinetic/statistical values in this review excerpt | Reinforces **extracellular/cell-surface-associated cellulosomal localization model** for dockerin-bearing enzymes in these bacteria (pqac-00000014) | (pqac-00000014), 2024, https://doi.org/10.1016/j.heliyon.2024.e24022 |


*Table: This table summarizes the key evidence available in the conversation for functional annotation of Ruminiclostridium josui Fae1A, integrating biochemical characterization with recent genomics and review context. It is useful for resolving the apparent annotation conflict by showing that published evidence supports a secreted, dockerin-bearing CE1 feruloyl esterase rather than a cellulase.*