238 p. J. KELLER, G. T. CORI VOL. 12 (1953) 



for ascending and descending limbs of the diffusion cell and the curves were symmetrical 

 between 138 and 4000 minutes. 



In retrospect it would seem that during Oncley's measurements phosphorylase a 

 was being converted to h by traces of PR which may adhere to phosphorylase even 

 through several recrystallizations. 



How the PR enzyme effects the halving of phosphorylase a is the subject of further 

 investigation. While prosthetic group-removing enzyme is a misnomer, it is proposed to 

 retain the name PR (phosphorylase-rupturing enzyme). In chromatographic experi- 

 ments neither peptide fragments nor free amino acids were found to be released in the 

 atoh conversion. It may be recalled that crystalline trypsin will convert phosphorylase 

 a to a form enzymically identical with phosphorylase W-. At pH 6 this reaction proceeds 

 preferentially to general proteolysis. However, the PR enzyme shows neither proteolytic 

 nor esteratic activity when tested with substrates which are acted upon by trypsin. The 

 identity or non-identity of trypsin-formed phosphorylase h and the PR product is also 

 being investigated. 



Miss Carmelita Lowry's technical assistance is gratefully acknowledged. 



SUMMARY 



Phosphorylase 6, the product of the action of a muscle enzyme (PR) on crystalline rabbit muscle 

 phosphorylase a, has one half the molecular weight of the a form. The molecular weights are 242,000 

 and 495,000 respectively. 



r£sum£ 



La phosphorylase h, produite par Taction d'un enzyme du muscle (PR) sur la phosphorylase a 

 cristallisee du muscle de lapin, a un poids moleculaire inferieure de moitie de celui de la forme a. 

 Les poids moleculaircs sont respectivement 242,000 et 495,000. 



ZUSAMMENFASSUNG 



Das Produkt der Einwirkung eines Muskelenzyms (PR) auf kristalline Kaninchenmuskel- 

 phosphorylase a, die Phosphorylase h hat die Halfte des Molekulargewichts der a-Form. DieMolekular- 

 gewichte sind 242,000 bzw. 495,000. 



REFERENCES 



^ G. T. CoRi AND A. A. Green, /. Biol. Chem., 151 (1943) 31. 



2 G. T. CoRi AND C. F. CoRi, J . Biol. Chem., 158 (1944) 321. 



^ S. F. Velick and L. F. Wicks, /. Biol. Chem., 190 (1951) 741. 



■* J. L. Oncley, /. Biol. Chem., 151 (1943) 21. 



^ A. A. Green,/. Biol. Chem., 158, (1944) 315. 



® J. F. Taylor, Federation Proc., 9 (1950) No. i. 



Received April 23, 1953 



