VOL. 12 (1953) HEAT OF HYDROLYSIS OF TRIMETAPHOSPHATE I23 



Studies on the enzyme 



The optimum hydrogen ion concentration of enzymichydrolysis of trimetaphosphate 

 was investigated between pH 4.25 and 9 and found to occur at a pH of approximately 7. 

 This observation agrees with findings of Schaffner and Krumey using enzyme extracts 

 from dried ^^east^^ and Neuberg and Fischer who prepared the enzyme from Aspergillus 

 oryzae^^. However, both authors used tripolyphosphate as substrate. On the contrary, 

 metaphosphatase prepared from Aspergillus niger showed a pH optimum of approxi- 

 mately 4 ^''^^, except for some mutant strains, enzyme extracts of which attained 

 maximum activity at pH 6-^. 



The activation of the enzyme by some divalent metallic ions in 2-io~^ M con- 

 centration at pH 7 is summarized in Table I. Bamann and Heumuller found that the 



enzyme prepared from liver was activated ten times more by Mn++2^. As our findings 

 show, the enzyme of yeast is almost equally well activated either by Mn++ or Mg++. 



The action of various inhibitors as azide, arsenate, KCN, NaF and glutathione is 

 given in Table II. 



TABLE II 



INHIBITION OF ENZYME BY VARIOUS INHIBITORS 



Inhibitor Final Concentration ^""^^^ '"'' "f f »"^J' 



m percent 



The results indicate that at this level of purity, the enzyme is appreciabl}- inhibited 

 only b}' fluoride and cyanide. 



The activity of the enzyme with trimetaphosphate, hexametaphosphate and pyro- 

 phosphate in equimolar concentrations as substrate at pH 7 is recorded in Table III. 



This nonspecificity of pyro- and metaphosphatase preparations of yeast even after 

 a thousandfold purification was discussed recently by Hoffman-Ostenhof^*. 



References p. 127. 



