No abstract

No abstract

TRUE SUBSTRATES FOR ALKALINE PHOSPHATASE 19 o.o16 M/~-glycerophosphate where it might be assumed that substrate formation is fast enough so that it is no longer rate-controlling. In addition to the cases above, Ross and his associates 3 have reported variation in pH optima for alkaline phosphatase activity with substrate concentration for phenyl disodium phosphate, adenylic acid, fructose-I,6-diphosphate, fructose-6-phosphate, and ribonucleic acid. The same analysis may be applied to these; and the "true" substrate may be selected as that which demonstrates an optimum concentration invariant with pH change. It was found that the optimum concentration was constant when the un-ionized acid form was picked as the substrate for all cases but ribonucleic acid, where the monovalent ion showed invariance. SUMMARY In the enzymic hydrolysis of/~-glycerophosphate, the species on which the alkaline phosphatase acts is the un-ionized acid. Supporting evidence for this includes: (a) 82p specific activity of the hydrolysis product corresponding to the specific activity of the un-ionized acid in the reaction medium; (b) an increase in reactivity with enzyme dilution which disappears with lower pH; and (c) experimental data from the literature.

No abstract

No abstract