pelA (PA3064, Q9HZE4) notes

Identity

PelA, 948 aa, multidomain periplasmic Pel-modification enzyme: N-terminal
GH166 (GH114-like TIM-barrel, Pfam PF03537, residues 68-296) glycoside
hydrolase domain and a C-terminal CE21 carbohydrate esterase (deacetylase)
domain (residues 520-804). Unreviewed TrEMBL entry with no curated comments.
PANTHER PTHR35882 "PELA". First gene of the pelA-pelG operon.
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Literature

PseudoCAP seed paper (Colvin et al. 2013, full text): purified PelA hydrolyses
the pseudosubstrate p-nitrophenyl acetate; active-site point mutants lose
activity and Pel-dependent biofilm/wrinkly colonies
PMID:23504011;
PMID:23504011;
fractionation places PelA in periplasmic and membrane fractions
PMID:23504011.
PelA-PelB complex: the PelB TPR domain binds PelA directly in the periplasm,
raising deacetylase and lowering hydrolase activity
PMID:28972168.
Structure (2025): Pel is a partially deacetylated alpha-1,4 GalNAc polymer;
PelA deacetylates and hydrolyses it before export; the deacetylase domain
founds carbohydrate esterase family CE21; the hydrolase domain is an
endo-alpha-1,4-N-acetylgalactosaminidase
PMID:40120681;
PMID:40120681;
PMID:40120681.

Interpretation

The specific MF is GO:0047375 N-acetylgalactosaminoglycan deacetylase activity
(is_a deacetylase activity): PelA removes acetyl groups from GalNAc in the Pel
polymer and from alpha-1,4-GalNAc oligosaccharides. The hydrolase activity on
alpha-1,4-GalNAc has no exact GO term (GO:0033931 endogalactosaminidase is for
deacetylated poly-GalN), so it is raised as a question rather than annotated.
Biofilm formation is a downstream outcome of Pel production.

Node leaf check (PTN002441861)

UniProt records of the other two leaves (retrieved 2026-10-28 via UniProt REST):

leaf	organism	length	domains
Q9HZE4 PelA	P. aeruginosa PAO1	948 aa	GH114 TIM barrel (68-296) + CE21 deacetylase (520-804)
B8DZ50 Dtur_0372	Dictyoglomus turgidum	518 aa	GH114 TIM barrel (51-259) + CARDB (432-514)
Q9RWG2 DR_0706	Deinococcus radiodurans	252 aa	TIM barrel only

Neither non-Pseudomonas leaf is long enough to contain the 520-804 deacetylase
domain, so the deacetylase IBD at this node is attached to a family defined by
the hydrolase domain. Domain mapping was from UniProt/InterPro features only, not
an alignment.

PseudoCAP IBA-seed assessment

PTN node	node term	n_seeds	leaf IBAs	seed annotation (term, evidence, PMID)	verdict	rationale
PTN002441861	GO:0019213 deacetylase activity	1 (sole seed)	3 (3 taxa)	GO:0019213 deacetylase activity, IDA, PMID:23504011 (PseudoCAP)	SOUND	Direct assay of purified PelA (pNP-acetate esterase activity lost in active-site mutants), later confirmed on GalNAc oligosaccharides (PMID:40120681). The seed is sound for PelA. The node term does not suit the clade: the two other leaves (Dictyoglomus B8DZ50, 518 aa; Deinococcus Q9RWG2, 252 aa) contain only the GH114-like hydrolase domain and lack the CE21 deacetylase domain (PelA residues 520-804), so they cannot inherit the activity. A GO_CENTRAL defect asks for the IBD to be restricted to deacetylase-domain-containing PelA orthologs.

Decisions summary

MODIFY: deacetylase activity (IBA, IDA) -> N-acetylgalactosaminoglycan
deacetylase activity (GO:0047375); carbohydrate metabolic process (IEA) ->
polysaccharide biosynthetic process.
ACCEPT: polysaccharide biosynthetic process (TAS).
KEEP_AS_NON_CORE: single-species biofilm formation (IMP).
NEW: periplasmic space (IDA, PMID:23504011).
GO_CENTRAL defect (PROBABLE): deacetylase IBD on leaves lacking the domain.
No PSEUDOCAP defect.