Phosphorylase

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 phosphonate group from a donor using water, whereas a kinase transfers a phosphonate 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 $\rightleftharpoons$ A-OP + H-B	transfer group = A = glycosyl- group or nucleotidyl- group
Phosphatase	Hydrolase (EC 3)	P-B + H-OH $\rightleftharpoons$ P-OH + H-B
Kinase	Transferase (EC 2.7.1-2.7.4)	P-B + H-A $\rightleftharpoons$ 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 active form of glycogen phosphorylase that is derived from the phosphorylation of the inactive form, phosphorylase b.

Pathology

Some disorders are related to phosphorylases:

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

References

↑ Lehninger Principles of Biochemistry 5th ed. pg. 603

External links

Muscle phosphorylase deficiency - McArdle's Disease Website
Phosphorylases at the US National Library of Medicine Medical Subject Headings (MeSH)

Transferases: phosphorus-containing groups (EC 2.7)

2.7.1-2.7.4:
phosphotransferase/kinase
(PO₄)

2.7.1: OH acceptor	Hexo- Gluco- Fructo- Hepatic Galacto- Phosphofructo- 1 Liver Muscle Platelet 2 Riboflavin Shikimate Thymidine ADP-thymidine NAD⁺ Glycerol Pantothenate Mevalonate Pyruvate Deoxycytidine PFP Diacylglycerol Phosphoinositide 3 Class I PI 3 Class II PI 3 Sphingosine Glucose-1,6-bisphosphate synthase

2.7.2: COOH acceptor	Phosphoglycerate Aspartate kinase

2.7.3: N acceptor	Creatine

2.7.4: PO₄ acceptor	Phosphomevalonate Adenylate Nucleoside-diphosphate Uridylate Guanylate Thiamine-diphosphate

2.7.6: diphosphotransferase
(P₂O₇)

2.7.7: nucleotidyltransferase
(PO₄-nucleoside)

Polymerase

DNA polymerase	DNA-directed DNA polymerase I II III IV V RNA-directed DNA polymerase Reverse transcriptase Telomerase DNA nucleotidylexotransferase/Terminal deoxynucleotidyl transferase

RNA nucleotidyltransferase	RNA polymerase/DNA-directed RNA polymerase RNA polymerase I RNA polymerase II RNA polymerase III RNA polymerase IV Primase RNA-dependent RNA polymerase PNPase

Phosphorolytic
3' to 5' exoribonuclease

Nucleotidyltransferase

Guanylyltransferase

mRNA capping enzyme

Other

2.7.8: miscellaneous

Phosphatidyltransferases	CDP-diacylglycerol—glycerol-3-phosphate 3-phosphatidyltransferase CDP-diacylglycerol—serine O-phosphatidyltransferase CDP-diacylglycerol—inositol 3-phosphatidyltransferase CDP-diacylglycerol—choline O-phosphatidyltransferase

Glycosyl-1-phosphotransferase	N-acetylglucosamine-1-phosphate transferase

2.7.10-2.7.13: protein kinase
(PO₄; protein acceptor)

2.7.10: protein-tyrosine	see tyrosine kinases

2.7.11: protein-serine/threonine	see serine/threonine-specific protein kinases

2.7.12: protein-dual-specificity	see serine/threonine-specific protein kinases

2.7.13: protein-histidine	Protein-histidine pros-kinase Protein-histidine tele-kinase Histidine kinase

Transferases: glycosyltransferases (EC 2.4)

2.4.1: Hexosyl-
transferases

Glucosyl-	Phosphorylase Starch Glycogen Myo- Glycogen synthase Debranching enzyme Branching enzyme 1,3-Beta-glucan synthase Ceramide glucosyltransferase

Galactosyl-	Lactose synthase B-N-acetylglucosaminyl-glycopeptide b-1,4-galactosyltransferase Glycoprotein-N-acetylgalactosamine 3-beta-galactosyltransferase (C1GALT1)

Glucuronosyl-	B3GAT1 B3GAT2 B3GAT3 UGT1A1 UGT1A3 UGT1A4 UGT1A5 UGT1A6 UGT1A7 UGT1A8 UGT1A9 UGT1A10 UGT2A1 UGT2A2 UGT2A3 UGT2B4 UGT2B7 UGT2B10 UGT2B11 UGT2B15 UGT2B17 UGT2B28 Hyaluronan synthase: HAS1 HAS2 HAS3

Fucosyl-	POFUT1 POFUT2 FUT1 FUT2 FUT3 FUT4 FUT5 FUT6 FUT7 FUT8 FUT9 FUT10 FUT11

Mannosyl-	Dolichyl-phosphate-mannose-protein mannosyltransferase POMT1 POMT2 DPM1 DPM3 ALG1 ALG2 ALG3 ALG6 ALG8 ALG9 ALG12

2.4.2: Pentosyl-
transferases

Ribose

ADP-ribosyltransferase	NAD⁺:diphthamide ADP-ribosyltransferase Diphtheria toxin NAD(P)⁺:arginine ADP-ribosyltransferase Pertussis toxin Cholera toxin Poly ADP ribose polymerase Sirtuin

Phosphoribosyltransferase	Adenine phosphoribosyltransferase Hypoxanthine-guanine phosphoribosyltransferase Uracil phosphoribosyltransferase Amidophosphoribosyltransferase

Other	Purine nucleoside phosphorylase: Thymidine phosphorylase ECGF1