Abstract
Two forms of tartrate-sensitive acid phosphatases (EC 3.1.3.2) were purified from rabbit kidney cortex by a multiple-column-chromatography method. The basic form constituted 90% of the enzyme and migrated as a single band of protein on polyacrylamide-gel electrophoresis. The proteins contaminating the acidic form did not exceed 5% of the total protein. The specific activity towards p-nitrophenyl phosphate was 12 mumol/min per mg for the basic form and 0.7 mumol/min per mg for the acidic form. The basic form of the enzyme differs from the acidic form in its heat-stability, Km values, inhibition rates by tartrate and fluoride and substrate specificities. Relative to p-nitrophenyl phosphate hydrolysis rate, the acidic form hydrolysed a variety of physiological monophosphate esters, whereas the basic form hydrolysed only CMP and phosphoenolpyruvate. Bacterial neuraminidases had no effect on the activity and mobility of the acidic form on polyacrylamide-gel electrophoresis. Both forms have the same molecular weight (101000 +/- 4000) and are probably composed of two identical subunits. The question whether the two forms of the enzyme are different proteins or whether one is a modified form of the other is discussed.