(myosin-light-chain) phosphatase

myosin-light-chain-phosphatase
Identifiers
EC number	3.1.3.53
CAS number	86417-96-1
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Gene Ontology	AmiGO / EGO
Search PMC articles PubMed articles

In enzymology, a myosin light-chain phosphatase (MLCP) (EC 3.1.3.53) is an enzyme that catalyzes the chemical reaction

[myosin light-chain] phosphate + H₂O $\rightleftharpoons$ [myosin light-chain] + phosphate

Thus, the two substrates of this enzyme are myosin light-chain phosphate and H₂O, whereas its two products are myosin light-chain and phosphate.

This enzyme belongs to the family of hydrolases, specifically those acting on phosphoric monoester bonds. The systematic name of this enzyme class is [myosin-light-chain]-phosphate phosphohydrolase. Other names in common use include myosin light chain kinase phosphatase, myosin phosphatase, myosin phosphatase, protein phosphatase 2A, and myosin-light-chain-phosphatase.

Structural studies

MLCP is composed of three subunits: a PP1c catalytic subunit, a myosin targeting subunit called MYPT1, and a small subunit of unknown function called M20.

As of late 2007, only one structure has been solved for this class of enzymes, with the PDB accession code 1S70.

Function

MLCP is important for regulating contraction in smooth muscle, which lacks the troponin binding system. It inhibits contraction by dephosphorylating myosin light-chain fibers. It counters the myosin light-chain kinase (MLCK), which promotes contraction by phosphorylating myosin light-chain proteins. MLCP is present in smaller amounts compared with MLCK, but compensates for this lack of mass by rapid movement along actin fibers. MLCP activity is inhibited by Rhoa and Rho kinase, components of the Ca²⁺ independent pathway for maintaining muscle contraction.^[1]

See also

• myosin
• myosin light-chain kinase
• Rhoa
• Rho kinase

References

1. ^ Michael P. Walsh, et all (2005). "Thromboxane A2-induced contraction of rat caudal arterial smooth muscle involves activation of Ca2+ entry and Ca2+sensitization: Rho-associated kinase-mediated phosphorylation of MYPT1 at Thr-855 but not Thr-697". Biochemical Journal 389 (Pt 3): 763–74. doi:10.1042/BJ20050237. PMC 1180727. PMID 15823093. http://biosupport.licor.com/docs/2005/BJ20050237.pdf. 

Further reading

• Pato MD, Adelstein RS (1983). "Purification and characterization of a multisubunit phosphatase from turkey gizzard smooth muscle. The effect of calmodulin binding to myosin light chain kinase on dephosphorylation". J. Biol. Chem. 258 (11): 7047–54. PMID 6304072. 
• Kimura K et al. (1996). "Regulation of Myosin phosphatase by Rho and Rho-associated kinase (Rho-kinase)". Science 273 (5272): 245–248. doi:10.1126/science.273.5272.245. PMID 8662509. 

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