“Phosphorylase”的意思、由来-开放百科全书

词条

Phosphorylase

释义

Function
Types
Activation
Pathology
See also
References
External links

{{Infobox enzyme
| Name = Phosphorylase
| EC_number = 2.4.1.1
| CAS_number = 9035-74-9
| IUBMB_EC_number = 2/4/1/1
| GO_code =
| image = 1z8d.jpg
| width = 270
| caption =
}}

Phosphorylases are enzymes that catalyze the addition of a phosphate group from an inorganic phosphate (phosphate+hydrogen) to an acceptor.

A-B + P {{eqm}} A + P-B

They include allosteric enzymes that catalyze the production of glucose-1-phosphate from a glucan such as glycogen, starch or maltodextrin. Phosphorylase is also a common name used for glycogen phosphorylase in honor of Earl W. Sutherland Jr. who in the late 1930s discovered the first phosphorylase.^[1]

Function

Phosphorylases should not be confused with phosphatases, which remove phosphate groups.

In more general terms, phosphorylases are enzymes that catalyze the addition of a phosphate group from an inorganic phosphate (phosphate + hydrogen) to an acceptor, not to be confused with a phosphatase (a hydrolase) or a kinase (a phosphotransferase). A phosphatase removes a phosphate group from a donor using water, whereas a kinase transfers a phosphate group from a donor (usually ATP) to an acceptor.

Enzyme name	Enzymes class	Reaction	Notes
Phosphorylase	Transferase (EC 2.4 and EC 2.7.7)	A-B + H-OP {{eqm}} A-OP + H-B	transfer group = A = glycosyl- group or nucleotidyl- group
Phosphatase	Hydrolase (EC 3)	P-B + H-OH {{eqm}} P-OH + H-B
Kinase	Transferase (EC 2.7.1-2.7.4)	P-B + H-A {{eqm}} P-A + H-B	transfer group = P
P = phosphonate group, OP = phosphate group, H-OP or P-OH = inorganic phosphate

Types

The phosphorylases fall into the following categories:

Glycosyltransferases (EC 2.4)
- Enzymes that break down glucans by removing a glucose residue (break O-glycosidic bond)
- glycogen phosphorylase
- starch phosphorylase
- maltodextrin phosphorylase
- Enzymes that break down nucleosides into their constituent bases and sugars (break N-glycosidic bond)
- Purine nucleoside phosphorylase (PNPase)
Nucleotidyltransferases (EC 2.7.7)
- Enzymes that have phosphorolytic 3' to 5' exoribonuclease activity (break phosphodiester bond)
- RNase PH
- Polynucleotide Phosphorylase (PNPase)

All known phosphorylases share catalytic and structural properties .

Activation

Phosphorylase a is the more active R form of glycogen phosphorylase that is derived from the phosphorylation of the less active R form, phosphorylase b with associated AMP. The inactive T form is either phosphorylated by phosphoylase kinase and inhibited by glucose, or dephosphorylated by phosphoprotein phosphatase with inhibition by ATP and/or glucose 6-phosphate. Phosphorylation requires ATP but dephosphorylation releases free inorganic phosphate ions.

Pathology

Some disorders are related to phosphorylases:

Glycogen storage disease type V - muscle glycogen
Glycogen storage disease type VI - liver glycogen

References

1. ^Lehninger Principles of Biochemistry 5th ed. pg. 603

External links

Muscle phosphorylase deficiency - McArdle's Disease Website
{{MeshName|Phosphorylases}}

{{Kinases}}{{Glycosyltransferases}}{{Enzymes}}{{Portal bar|Molecular and Cellular Biology|border=no}}{{2.4-enzyme-stub}}

2 : Transferases|EC 2.4.1

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