Enzyme

2.7.1.40 - Pyruvate kinase

Alternative Name(s)
  • Phosphoenol transphosphorylase.
  • Phosphoenolpyruvate kinase.

Catalytic Activity

ATP + pyruvate = ADP + H(+) + phosphoenolpyruvate

Cofactors

There are no Cofactors for this Enzyme

Reaction Mechanism

    pyruvate kinase By Reference

    Pyruvate kinase catalyses the final step of glycolysis and is allosterically regulated by fructose-1,6-bisphosphate. It requires two equivalents divalent cation, one of which binds to the enzyme as a complex with the nucleotide substrate, as well as activation by K+. As opposed to mammalian pyruvate kinase, the bacterial enzyme works in a K+ independent manner.

    The enzyme is also known to catalyse a variety of side reactions, including the decarboxylation of oxalacetate, the enolisation of pyruvate, ATP-dependent phosphorylation of alpha-hydroxy or alpha-thio carboxylates, ATP- and bicarbonate-dependent phosphorylations of fluoride and of hydroxylamine and to also function as an ATP- and bicarbonate-dependent ATPase. These side activities reflect the capacity of the active site to labilise the gamma-phosphate of ATP or to stabilise the enolate of pyruvate [PMID:9308890].

    There are four isozymes of pyruvate kinase in mammals (L, R, M1, M2) encoded by two different genes: PKLR and PKM. The L and R isozymes are generated from the PKLR by differential splicing of RNA; the M1 and M2 forms are produced from the PKM gene by differential splicing. L type is major isozyme in the liver, R is found in red cells, M1 is the main form in muscle, heart and brain, and M2 is found in early fetal tissues as well as in most cancer cells. This entry represents the PKM gene products.


    The reaction of pyruvate kinase is a two step reaction. In the first reaction the phosphate group of PEP is transferred to ADP to produce ATP. The bound enol is then protonated to produce pyruvate in its keto form.
    Catalytic Residues
    AA Uniprot Uniprot Resid PDB PDB Resid
    Arg P11974 73 1pkn 72
    Lys P11974 270 1pkn 269
    Thr P11974 328 1pkn 327
    Arg P11974 120 1pkn 119
    Step Components

    overall product formed, overall reactant used, proton transfer, intermediate formation, bimolecular nucleophilic substitution, native state of enzyme regenerated, dephosphorylation, intermediate collapse

    Step 1.

    Phosphoryl transfer from PEP to M(II)ADP occurs by an apparent SN2 mechanism with an inversion of configuration at the phosphoryl group, to yield the enolate of pyruvate and M(II)ATP. The presence of either a Mn or Mg divalent cation is essential for catalytic activity [PMID:8193145]. The monovalent cation, K+, does not directly contact the substrate or intermediate, but instead is thought to influence the structure of the active site though interactions with the positively charged resides Arg72, Arg119 and Lys269 [PMID:8193145].

    Step 2.

    Thr237 and the Mn(II) cation increase the acidity of water through hydrogen bonding and charge stabilisation, respectively, generating a specific acid to act towards the enolate intermediate. A solvent molecule at the active site stereospecifically protonates the enolate at the 2-si face of the double bond to form keto pyruvate. Kinetic and pH studies have shown the proton to originate from a solvent molecule [PMID:15568816]. The divalent cation is thought to enhance the acidity of the solvent molecule, rather than the monovalent cation [PMID:12562754].

    Products.

    The products of the reaction.

Reaction Parameters

There are no kinetic parameters information for this Enzyme

Associated Proteins

Protein name Organism
Pyruvate kinase 2, cytosolic Rice
Pyruvate kinase isozyme A, chloroplastic Common tobacco
Plastidial pyruvate kinase 3, chloroplastic Mouse-ear cress
Pyruvate kinase 2 Trypanosoma brucei brucei
Pyruvate kinase PKLR Human

Citations