ATP:guanido phosphotransferase family
Encyclopedia
In molecular biology, the ATP:guanido phosphotransferase family is a family of structurally and functionally related enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

s, that reversibly catalyse the transfer of phosphate
Phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...

 between ATP and various phosphogens. The enzymes belonging to this family include:
  • Glycocyamine kinase , which catalyses
    Catalysis
    Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....

     the transfer of phosphate from ATP to guanidoacetate.

  • Arginine kinase
    Arginine kinase
    In enzymology, an arginine kinase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are ATP and L-arginine, whereas its two products are ADP and Nomega-phospho-L-arginine....

     , which catalyses
    Biocatalysis
    Biocatalysis is the use of natural catalysts, such as protein enzymes, to perform chemical transformations on organic compounds. Both enzymes that have been more or less isolated and enzymes still residing inside living cells are employed for this task....

     the transfer of phosphate from ATP to arginine.

  • Taurocyamine kinase
    Taurocyamine kinase
    In enzymology, a taurocyamine kinase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are ATP and taurocyamine, whereas its two products are ADP and N-phosphotaurocyamine....

     , an annelid-specific enzyme that catalyses the transfer of phosphate from ATP to taurocyamine.

  • Lombricine kinase
    Lombricine kinase
    In enzymology, a lombricine kinase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are ATP and lombricine, whereas its two products are ADP and N-phospholombricine....

     , an annelid-specific enzyme that catalyses the transfer of phosphate from ATP to lombricine.

  • Smc74, a cercaria-specific enzyme from Schistosoma mansoni.

  • Creatine kinase
    Creatine kinase
    Creatine kinase , also known as creatine phosphokinase or phospho-creatine kinase , is an enzyme expressed by various tissues and cell types. CK catalyses the conversion of creatine and consumes adenosine triphosphate to create phosphocreatine and adenosine diphosphate...

      (CK), which catalyses the reversible transfer of high energy
    Energy
    In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

     phosphate from ATP to creatine, generating phosphocreatine and ADP.


Creatine kinase plays an important role in energy metabolism of vertebrates. There are at least four different, but very closely related, forms of CK. Two isozymes, M (muscle) and B (brain), are cytosolic, while the other two are mitochondrial
Mitochondrion
In cell biology, a mitochondrion is a membrane-enclosed organelle found in most eukaryotic cells. These organelles range from 0.5 to 1.0 micrometers in diameter...

. In sea urchin
Sea urchin
Sea urchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, or "test", is round and spiny, typically from across. Common colors include black and dull...

s there is a flagellar isozyme, which consists of the triplication of a CK-domain. A cysteine
Cysteine
Cysteine is an α-amino acid with the chemical formula HO2CCHCH2SH. It is a non-essential amino acid, which means that it is biosynthesized in humans. Its codons are UGU and UGC. The side chain on cysteine is thiol, which is polar and thus cysteine is usually classified as a hydrophilic amino acid...

 residue
Residue (chemistry)
In chemistry, residue is the material remaining after a distillation or an evaporation, or to a portion of a larger molecule, such as a methyl group. It may also refer to the undesired byproducts of a reaction....

 is implicated in the catalytic activity of these enzymes and the region around this active site
Active site
In biology the active site is part of an enzyme where substrates bind and undergo a chemical reaction. The majority of enzymes are proteins but RNA enzymes called ribozymes also exist. The active site of an enzyme is usually found in a cleft or pocket that is lined by amino acid residues that...

 residue is highly conserved.

ATP:guanido phosphotransferases contain a C-terminal catalytic domain which consists of a duplication where the common core consists of two beta-alpha-beta2-alpha repeat
Tandem repeat
Tandem repeats occur in DNA when a pattern of two or more nucleotides is repeated and the repetitions are directly adjacent to each other. -Example:An example would be:in which the sequence A-T-T-C-G is repeated three times.-Terminology:...

s. The substrate binding site
Binding site
In biochemistry, a binding site is a region on a protein, DNA, or RNA to which specific other molecules and ions—in this context collectively called ligands—form a chemical bond...

 is located in the cleft between N and C-terminal domains, but most of the catalytic
Biocatalysis
Biocatalysis is the use of natural catalysts, such as protein enzymes, to perform chemical transformations on organic compounds. Both enzymes that have been more or less isolated and enzymes still residing inside living cells are employed for this task....

 residues are found in the larger C-terminal domain. They also contain an N-terminal domain which has an all-alpha fold
Protein folding
Protein folding is the process by which a protein structure assumes its functional shape or conformation. It is the physical process by which a polypeptide folds into its characteristic and functional three-dimensional structure from random coil....

 consisting of an irregular array of 6 short helices
Alpha helix
A common motif in the secondary structure of proteins, the alpha helix is a right-handed coiled or spiral conformation, in which every backbone N-H group donates a hydrogen bond to the backbone C=O group of the amino acid four residues earlier...

.
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