The high molecular weight and the low molecular weight acid phosphatases of the frog liver and their phosphotyrosine activity.

1. Two molecular weight classes of non-specific acid phosphatases (AcPases) (3.1.3.2) are present in the frog (Rana esculenta) liver: a higher molecular weight (HMW) of Mr 140,560 and a lower molecular weight (LMW) of Mr 38,180 enzyme. 2. The LMW AcPase was described earlier and the HMW AcPase of optimum pH 4.8 is shown to be a L(+)-tartrate sensitive, thermolabile, dimeric glycoenzyme slightly activated by DTT. 3. The HMW and the LMW AcPases exhibit activity for phosphotyrosine which showed similar sensitivity to various effectors as the p-nitrophenyl phosphatase activity; however, both enzymes differed substantially in this respect suggesting that they might be involved in different metabolic steps.