Acid phosphatases in the frog ( Rana esculenta) skeletal muscle. Purification and some properties of the low molecular weight enzyme

Abstract

1. 1. The presence of high-Mr and low-Mr acid phosphatases [orthophosphoric-monoester phosphohydrolase, (add optimum), EC 3.1.3.2] in the skeletal muscle of frog Rana esculenta was reported. 2. 2. The subcellular localization and some characteristics of both enzymes were also described. 3. 3. The low-Mr AcPase was purified to homogeneity. The enzyme did not absorb on Concanavaline A-Sepharose 4B indicating that this was not a glycoprotein. 4. 4. The enzyme is homogeneous on polyacrylamide gel electrophoresis and moves as a single band of Mr 13.7 ±0.8 kDa in the presence of sodium dodecyl sulphate. 5. 5. The Mr of the native enzyme was 14.0 ± 1.1 kDa as determined by gel filtration on a Sephadex G-100 column. The isoelectric point was 6.02. 6. 6. The enzyme was strongly inhibited by l mM Ag +, Hg 2+, Sn 2+ and Cu 2+ while other cations both at 10 −2 and 10 −3 M showed little or no effect. 7. 7. The enzyme was insensitive to NaF and tartrate but was strongly deactivated by formaldehyde, PMB, lodoacetamide and Triton X-100. Phosphate was a competitive inhibitor ( k 1 = 0.83mM). 8. 8. The best substrate for the enzyme was p-nitrophenylphosphate but phenylphosphate, flavine mononucleotide and o-P-tyrosine were also hydrolyzed, though at different rates. 9. 9. The enzyme activity was enhanced in the presence of methanol, ethanol, acetone and glycerol indicating a phosphotransferase activity.