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1  structure 511  species 0  interactions 1047  sequences 18  architectures

Family: Arylesterase (PF01731)

Summary: Arylesterase

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Arylesterase Provide feedback

This family consists of arylesterases (Also known as serum paraoxonase) EC: These enzymes hydrolyse organophosphorus esters such as paraoxon and are found in the liver and blood. They confer resistance to organophosphate toxicity [1]. Human arylesterase (PON1) P27169 is associated with HDL and may protect against LDL oxidation [2].

Literature references

  1. Rodrigo L, Gil F, Hernandez AF, Marina A, Vazquez J, Pla A; , Biochem J 1997;321:595-601.: Purification and characterization of paraoxon hydrolase from rat liver. PUBMED:9032442 EPMC:9032442

  2. Primo-Parmo SL, Sorenson RC, Teiber J, La Du BN; , Genomics 1996;33:498-507.: The human serum paraoxonase/arylesterase gene (PON1) is one member of a multigene family. PUBMED:8661009 EPMC:8661009

Internal database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR002640

The serum paraoxonases/arylesterases are enzymes that catalyse the hydrolysis of the toxic metabolites of a variety of organophosphorus insecticides. The enzymes hydrolyse a broad spectrum of organophosphate substrates, including paraoxon and a number of aromatic carboxylic acid esters (e.g., phenyl acetate), and hence confer resistance to organophosphate toxicity [ PUBMED:8661009 ].

Mammals have 3 distinct paraoxonase types, termed PON1-3 [ PUBMED:8661009 , PUBMED:11038162 ]. In mice and humans, the PON genes are found on the same chromosome in close proximity. PON activity has been found in variety of tissues, with highest levels in liver and serum - the source of serum PON is thought to be the liver. Unlike mammals, fish and avian species lack paraoxonase activity.

Human and rabbit PONs appear to have two distinct Ca2+ binding sites, one required for stability and one required for catalytic activity. The Ca2+ dependency of PONs suggests a mechanism of hydrolysis where Ca2+ acts as the electrophillic catalyst, like that proposed for phospholipase A2. The paraoxonase enzymes, PON1 and PON3, are high density lipoprotein (HDL)- associated proteins capable of preventing oxidative modification of low density lipoproteins (LPL) [ PUBMED:11038162 ]. Although PON2 has oxidative properties, the enzyme does not associate with HDL.

Within a given species, PON1, PON2 and PON3 share ~60% amino acid sequence identity, whereas between mammalian species particular PONs (1,2 or 3) share 79-90% identity at the amino acid level. Human PON1 and PON3 share numerous conserved phosphorylation and N-glycosylation sites; however, it is not known whether the PON proteins are modified at these sites, or whether modification at these sites is required for activity in vivo [ PUBMED:11038162 ].

This family consists of arylesterases (Also known as serum paraoxonase) EC . These enzymes hydrolyse organophosphorus esters such as paraoxon and are found in the liver and blood. They confer resistance to organophosphate toxicity [ PUBMED:9032442 ]. Human arylesterase (PON1) SWISSPROT is associated with HDL and may protect against LDL oxidation [ PUBMED:8661009 ].

Gene Ontology

The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.

Domain organisation

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Pfam Clan

This family is a member of clan Beta_propeller (CL0186), which has the following description:

This large clan contains proteins that contain beta propellers. These are composed of between 6 and 8 repeats. The individual repeats are composed of a four stranded sheet. The clan includes families such as WD40 Pfam:PF00400 where the individual repeats are modeled. The clan also includes families where the entire propeller is modeled such as Pfam:PF02239 usually because the individual repeats are not discernible. These proteins carry out a very wide diversity of functions including catalysis.

The clan contains the following 88 members:

ANAPC4_WD40 APMAP_N Arylesterase Arylsulfotran_2 Arylsulfotrans B_lectin BBS2_Mid Beta_propel Coatomer_WDAD CPSF_A CyRPA Cytochrom_D1 Dpp_8_9_N DPPIV_N DPPIV_rep DUF1513 DUF1668 DUF2415 DUF3748 DUF4221 DUF4933 DUF4934 DUF5046 DUF5050 DUF5122 DUF5128 DUF5711 DUF839 eIF2A FG-GAP FG-GAP_2 FG-GAP_3 Frtz Ge1_WD40 Glu_cyclase_2 Gmad1 GSDH Hyd_WA IKI3 Itfg2 Kelch_1 Kelch_2 Kelch_3 Kelch_4 Kelch_5 Kelch_6 Lactonase Ldl_recept_b LGFP Lgl_C LVIVD Me-amine-dh_H MgpC MRJP Nbas_N Neisseria_PilC NHL nos_propeller nos_propeller_2 Nucleoporin_N Nup160 PALB2_WD40 PD40 Pectate_lyase22 Peptidase_S9_N PHTB1_N Phytase-like PQQ PQQ_2 PQQ_3 RAG2 RCC1 RCC1_2 Reg_prop SBBP SBP56 SdiA-regulated SGL Str_synth TcdB_toxin_midN Tectonin TolB_like VID27 WD40 WD40_2 WD40_3 WD40_4 WD40_like


We store a range of different sequence alignments for families. As well as the seed alignment from which the family is built, we provide the full alignment, generated by searching the sequence database (reference proteomes) using the family HMM. We also generate alignments using four representative proteomes (RP) sets and the UniProtKB sequence database. More...

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We make a range of alignments for each Pfam-A family. You can see a description of each above. You can view these alignments in various ways but please note that some types of alignment are never generated while others may not be available for all families, most commonly because the alignments are too large to handle.

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You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.

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HMM logos is one way of visualising profile HMMs. Logos provide a quick overview of the properties of an HMM in a graphical form. You can see a more detailed description of HMM logos and find out how you can interpret them here. More...


This page displays the phylogenetic tree for this family's seed alignment. We use FastTree to calculate neighbour join trees with a local bootstrap based on 100 resamples (shown next to the tree nodes). FastTree calculates approximately-maximum-likelihood phylogenetic trees from our seed alignment.

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Curation and family details

This section shows the detailed information about the Pfam family. You can see the definitions of many of the terms in this section in the glossary and a fuller explanation of the scoring system that we use in the scores section of the help pages.

Curation View help on the curation process

Seed source: Pfam-B_2101 (release 4.1)
Previous IDs: none
Type: Repeat
Sequence Ontology: SO:0001068
Author: Bashton M , Bateman A , Fenech M
Number in seed: 6
Number in full: 1047
Average length of the domain: 85.00 aa
Average identity of full alignment: 37 %
Average coverage of the sequence by the domain: 23.46 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 57096847 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 21.3 21.3
Trusted cut-off 21.3 21.3
Noise cut-off 21.2 21.2
Model length: 86
Family (HMM) version: 22
Download: download the raw HMM for this family

Species distribution

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Archea Archea Eukaryota Eukaryota
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Viruses Viruses Unclassified Unclassified
Viroids Viroids Unclassified sequence Unclassified sequence


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For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the Arylesterase domain has been found. There are 1 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein sequence.

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