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297  structures 18461  species 5  interactions 25953  sequences 52  architectures

Family: PK (PF00224)

Summary: Pyruvate kinase, barrel domain

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Pyruvate kinase, barrel domain Provide feedback

This domain of the is actually a small beta-barrel domain nested within a larger TIM barrel. The active site is found in a cleft between the two domains.

Literature references

  1. Larsen TM, Benning MM, Wesenberg GE, Rayment I, Reed GH; , Arch Biochem Biophys 1997;345:199-206.: Ligand-induced domain movement in pyruvate kinase: structure of the enzyme from rabbit muscle with Mg2+, K+, and L-phospholactate at 2.7 A resolution. PUBMED:9308890 EPMC:9308890

Internal database links

External database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR015793

Pyruvate kinase (EC) (PK) catalyses the final step in glycolysis [PUBMED:2379684], the conversion of phosphoenolpyruvate to pyruvate with concomitant phosphorylation of ADP to ATP:

ADP + phosphoenolpyruvate = ATP + pyruvate

The enzyme, which is found in all living organisms, requires both magnesium and potassium ions for its activity. In vertebrates, there are four tissue-specific isozymes: L (liver), R (red cells), M1 (muscle, heart and brain), and M2 (early foetal tissue). In plants, PK exists as cytoplasmic and plastid isozymes, while most bacteria and lower eukaryotes have one form, except in certain bacteria, such as Escherichia coli, that have two isozymes. All isozymes appear to be tetramers of identical subunits of ~500 residues.

PK helps control the rate of glycolysis, along with phosphofructokinase (INTERPRO) and hexokinase (INTERPRO). PK possesses allosteric sites for numerous effectors, yet the isozymes respond differently, in keeping with their different tissue distributions [PUBMED:12798932]. The activity of L-type (liver) PK is increased by fructose-1,6-bisphosphate (F1,6BP) and lowered by ATP and alanine (gluconeogenic precursor), therefore when glucose levels are high, glycolysis is promoted, and when levels are low, gluconeogenesis is promoted. L-type PK is also hormonally regulated, being activated by insulin and inhibited by glucagon, which covalently modifies the PK enzyme. M1-type (muscle, brain) PK is inhibited by ATP, but F1,6BP and alanine have no effect, which correlates with the function of muscle and brain, as opposed to the liver.

The structure of several pyruvate kinases from various organisms have been determined [PUBMED:11960989, PUBMED:10751408]. The protein comprises three-four domains: a small N-terminal helical domain (absent in bacterial PK), a beta/alpha-barrel domain, a beta-barrel domain (inserted within the beta/alpha-barrel domain), and a 3-layer alpha/beta/alpha sandwich domain.

This entry represents the two barrel domains, the beta/alpha-barrel, and the beta-barrel inserted within it.

Gene Ontology

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

Domain organisation

Below is a listing of the unique domain organisations or architectures in which this domain is found. More...

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Pfam Clan

This family is a member of clan PK_TIM (CL0151), which has the following description:

This superfamily consists of a number of TIM barrel domains found in enzymes such as pyruvate kinase, malate synthase and citrate lyase.

The clan contains the following 11 members:

C-C_Bond_Lyase HpcH_HpaI ICL Malate_synthase Pantoate_transf PEP-utilizers_C PEP_hydrolase PEP_mutase PEPcase PEPcase_2 PK


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 using the family HMM. We also generate alignments using four representative proteomes (RP) sets, the NCBI sequence database, and our metagenomics 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.

External links

MyHits provides a collection of tools to handle multiple sequence alignments. For example, one can refine a seed alignment (sequence addition or removal, re-alignment or manual edition) and then search databases for remote homologs using HMMER3.

HMM logo

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.

Note: You can also download the data file for the tree.

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: Prosite
Previous IDs: none
Type: Family
Author: Finn RD, Griffiths-Jones SR
Number in seed: 11
Number in full: 25953
Average length of the domain: 332.80 aa
Average identity of full alignment: 47 %
Average coverage of the sequence by the domain: 67.80 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 80369284 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 20.8 20.8
Trusted cut-off 20.8 20.8
Noise cut-off 20.7 20.7
Model length: 348
Family (HMM) version: 17
Download: download the raw HMM for this family

Species distribution

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Colour assignments

Archea Archea Eukaryota Eukaryota
Bacteria Bacteria Other sequences Other sequences
Viruses Viruses Unclassified Unclassified
Viroids Viroids Unclassified sequence Unclassified sequence


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This visualisation provides a simple graphical representation of the distribution of this family across species. You can find the original interactive tree in the adjacent tab. More...

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There are 5 interactions for this family. More...

PEP-utilizers PK_C PK_C PEP-utilizers PK


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 PK domain has been found. There are 297 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 seqence.

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