INHIBITION BY MACROIONS 461 



of gentisate with values around 2000-2500 (Hahn and Frank, 1953). Poly- 

 esters of phosphate with phloretin (or other polyphenols) are very inhibi- 

 tory to hyaluronidase, 0.005 mg/ml completely abolishing enzyme activity 

 (Diczfalusy et al., 1953). Phloroglucinol phosphate polymer may be even 

 more potent, 0.00013 mg/ml inhibiting 80% (Ferno et al, 1953). Such poly- 

 mers may be represented as: 



o- o- o- 



— 0— P— 0— R— 0— P— O— R— 0— P— O— 

 OH OH OH 



The extent of the inhibition may depend primarily on the distance between 

 anionic groups and the ability of the polymer to assume the appropriate 

 configurations on the enzyme surface. 



Ribonuclease 



Pancreatic ribonuclease is strongly and competitively inhibited by hep- 

 arin (Zollner and Fellig, 1952, 1953) but the results by different investigators 

 vary quite widely, due perhaps to different experimental conditions (espe- 

 cially pH and ionic strength), different preparations of heparin, and differ- 

 ent techniques for measuring the enzyme activity. The competitive nature 

 of the inhibition (at least the reduction in inhibition upon increasing RNA 

 concentration) has been confirmed by Roth (1953) and Houck (1957 b). 

 Increase in ionic strength reduces the inhibition as expected (Houck, 1957 b; 

 Heymann et al, 1958; Fellig and Wiley, 1959; Lorenz et al, 1960), although 

 Houck found some deviation from this at very high NaCl concentrations. 

 The results of Lorenz et al (1960) are quite typical (see accompanying 

 tabulation): 



Lowering the pH from around 7.5-8.0 to 5.0 progressively augments the 

 inhibition (Zollner and Fellig, 1953; Roth, 1953 b), which is perhaps a re- 

 flection of the increasing positive charge on the ribonuclease (isoelectric 

 point is 9.5). The ribonucleases of rat kidney and liver (Roth, 1953 b) and 

 rat and guinea pig serum (Rabinovitch and Dohi, 1957) are also inhibited 



