Hyaluronic acid binding was inferred from the Link domain InterPro signature IPR000538, which is confidently matched in this protein.

The root-level hydrolase activity annotation derives from the ARBA Hydrolase keyword. The keyword itself is defensible for TSG-6, whose heavy-chain transfer proceeds through an ester intermediate, but the term is far less informative than the carboxylesterase activity term used for the human orthologue.

Extracellular space and negative regulation of inflammatory response were propagated from the PANTHER TSG-6 subfamily PTHR46908:SF4. The human orthologue carries the inflammatory-response term from direct assay as well as by phylogenetic inference, so this propagation rests on experimental evidence rather than on prediction alone.

The cell adhesion annotation derives from combined automated methods applied to the Cell adhesion keyword; no experimental evidence for this process exists for TSG-6 in any species.

At least two TSG-6 family members are transcribed in D. rotundus salivary gland, and TSG-6 was confirmed in the principal gland proteome by LC-MS/MS (101 ions, the fourth most abundant protein family identified, after semaphorin at 855 ions, plasminogen activator at 597 and lipocalin at 163). This is the study whose EMBL submission (JAA46157.1, salivary gland) underlies the K9IIP0 accession.

The Link module is the hyaluronan-binding module that defines the hyaladherin family, and it is the N-terminal half of TSG-6.

TSG-6 suppresses neutrophil migration and inhibits inflammation in multiple in vivo models, which is the basis for the anti-inflammatory annotation.

TSG-6 potentiates the antiplasmin activity of inter-alpha-inhibitor through a Link module to bikunin interaction, linking the protein to fibrinolysis regulation as well as inflammation - potentially relevant in a saliva that also contains a plasminogen activator.

The function of the C-terminal CUB domain of TSG-6 remains unidentified. This is the domain to which the UniProt CAUTION for this protein is scoped.

The authors propose an anti-inflammatory role for the protein in bat saliva specifically, but state it as a possibility rather than a measurement.

TSG-6, acting with heavy chain 2, has a catalytic activity that transfers inter-alpha-inhibitor heavy chains onto hyaluronan. This is the direct experimental basis for the carboxylesterase activity term on the human orthologue and, by orthology, for the proposed replacement term here.

The reaction proceeds by two divalent cation-dependent transesterifications through a covalent TSG-6-heavy-chain intermediate, which is why the chemistry is transesterification rather than the net hydrolysis that GO:0106435 formally describes.

Heavy chains are transferred onto hyaluronan and can be further shuffled between glycosaminoglycans, so the activity covalently modifies hyaluronan itself - the basis of the proposed hyaluronan metabolic process annotation.

TSG-6 acts as a catalyst in the transfer of heavy chains from inter-alpha-inhibitor onto hyaluronan through covalent heavy-chain-TSG-6 intermediates, and is the only known transferase able to produce heavy chain-hyaluronan complexes.

The heavy chains are attached covalently to hyaluronan sugars, so the reaction is a covalent modification of the hyaluronan polymer and falls under hyaluronan metabolic process.

The heavy-chain transferase activity, rather than hyaluronan binding, is the activity required for cumulus-oocyte complex expansion in mice, establishing the catalytic function as physiologically load-bearing.

TSG-6 forms covalent complexes with inter-alpha-inhibitor and pre-alpha-inhibitor heavy chains and potentiates the antiplasmin activity of bikunin, corroborating both the covalent heavy-chain chemistry and the fibrinolysis link noted for the salivary protein.

The protein is TSG-6/TNFAIP6 with a signal peptide (1-17), a Link domain (36-129) carrying the 58-127 and 82-103 disulfides, and a CUB domain (135-247).

The record states that the ITIH2/HC2 interaction is required for transesterification of the inter-alpha-inhibitor heavy chain onto hyaluronan, which is the covalent catalytic step behind the carboxylesterase activity annotation of the human orthologue.

The Link module is also recorded as binding a broad panel of C-X-C and C-C chemokines, interfering with their binding to glycosaminoglycans - the mechanism of TSG-6's anti-inflammatory action.

The UniProt CAUTION is scoped to PROSITE ProRule PRU00059, which is the CUB domain rule (PROSITE PS01180). It therefore limits confidence in CUB-derived feature transfer, and does not bear on the Link module (rule PRU00323), on secretion, or on hyaluronan binding.

TSG-6 is a secreted inflammation-inducible glycoprotein whose Link module binds hyaluronan and other glycosaminoglycans, and which acts in the extracellular matrix and pericellular matrix.

The report enumerates enzymatic transesterase activity transferring inter-alpha-inhibitor heavy chains to hyaluronan among the biochemical activities of TSG-6, independently corroborating the catalytic call.

The report is explicit that direct bat-specific primary literature is limited and that its functional annotation is inferred from conserved domain architecture plus mammalian TSG-6 data.