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P1261 Sigma

Phosphorylase a from rabbit muscle

lyophilized powder, 20-30 units/mg protein

Synonym: 1,4-α-D-Glucan:orthophosphate α-D-glucosyltransferase



Related Categories 2.4.x.x Glycosyltransferases, 2.x.x.x Transferases, Biochemicals and Reagents, Cell Biology, Enzyme Class Index,
form   lyophilized powder
purified by   2× crystallization
composition   Protein, 30-60% E1%/280
foreign activity   AMP-phosphatase, ATP-phosphatase, debrancher enzyme and phosphorylase phosphatase ≤0.1%
  phosphoglucomutase ≤0.25%
  phosphorylase b ≤30%
storage temp.   −20°C


General description

Phosphorylase A is the active form of glycogen phosphorylase which converts glycogen and orthophosphate (Pi) to glucose 1-phoshate (G-1-P).


10, 25 mg in poly bottle

Unit Definition

One unit will form 1.0 μmole of α-D-glucose 1-phosphate from glycogen and orthophosphate per min at pH 6.8 at 30 °C, measured in a system containing phosphoglucomutase, NADP, and glucose-6-phosphate dehydrogenase. (One μmolar unit is equivalent to ~45 Cori units.)

Physical form

Lyophilized powder containing β-glycerophosphate and EDTA


Phosphorylase from rabbit muscle has been used in a study to assess the molecular mechanisms of oleanolic acid. It has also been used in a study to describe the conversion of phosphorylase B to A, through a conversion enzyme in the presence of 32P-ATP.

Biochem/physiol Actions

Dimeric phosphorylase b is converted to the more active tetramer, phosphorylase a, by the action of phosphorylase kinase.

Phosphorylase A can be inhibited by these compounds: Polychlorinated biphenyls, polychlorinated biphenylols and polybrominated biphenyls.

Price and Availability

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Safety & Documentation

Safety Information

NONH for all modes of transport
WGK Germany 

Frequently Asked Questions

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My question is not addressed here, how can I contact Technical Service for assistance?
Use the option to the right to "Ask a Question" by email of a Technical Service Scientist.
How is Phosphorylase A, Product P1261, prepared?
To prepare Phosphorylase A (P1261), Sigma uses a method similar to the one described in the J. Biol.Chem., 231, 65 (1958).
What is the final buffer Phosphorylase A, Product P1261, is in prior to lyophilization?
The final buffer Phosphorylase A (P1261) is in prior to lyophilization is 0.1M B-glycerophosphate and 4 mM EDTA.        
What is the solubility of Phosphorylase A, Product P1261?
Sigma tests solubility of Phosphorylase A (P1261) in water at a concentration of 1 mg/ml.   
What is the molecular weight of Phosphorylase A, Product P1261?
The molecular weight of Rabbit    Phosphorylase A (tetramer) is 370,000 per Biochemistry 6 (1967) p. 3315 (which was determined by sedimentation and "experiments in a variety of buffers, temperatures, and ionic strenght").  The molecular weight by sequence analysis (Proc. Natl. Acad. Sci. USA, 74, 4762-4766) is 97,412.             
What is the pI of Phosphorylase A, Product P1261?
The pI of Phosphorylase A (P1261) is 5.6 - 5.8.
Has the amino acid sequence of phosphorylase from rabbit muscle been published?
The sequence has been published. The amino acid composition is: Asp5l, Asn45, Thr35, Ser29, Glu64, Gln31, Pro36, Gly48, Ala63, Cys9, Val62, Met2l, Ile49, Leu79, Tyr36, Phe38, Trp12, Lys48, HiS22, and Arg63. Reference for the sequence and amino acid composition: K. Titani et al., Proc. Nat. Acad. Sci., USA, 74, 4762-4766 (1977) (see attached pdf). Product P1261 is phosphorylase a, which is the tetrameric form. Products P4649 and P6635 are phosphorylase b, the dimeric  form. The sequence information of the subunit would be the same for both forms.
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