Isolation of buffalo muscle aldolase and comparison of its properties with those of rabbit muscle aldolase .

Fructose-1,6-bisphosphate aldolase (D-fructose-1,6-bisphosphate D-glyceraldehyde-3-phyosphate-lyase, EC 4.1.2.13) was isolated from buffalo muscle by fractionation with ammonium sulphate and subsequent purification by phosphocellulose column chromatography using a linear salt gradient. As judged by gel filtration and electrophoresis in polyacrylamide gel, the enzyme was homogeneous with respect to size and charge. The molecular weight and Stokes radius of the enzyme were determined from its elution profile on a calibrated Sephadex column and the respective values were 162000 and 4.55 nm. The diffusion coefficient and frictional ratio were computed to be 4.8-10(7) cm2-s-1 and 1.27, respectively. The molecular weight of the polypeptide chain as measured by aodium dodecyl sulphate polyacrylamide gel electrophoresis was 40750. This taken together with the native molecular weight suggested a four-subunit model for the protein. The N- AND C-terminal residues of polypeptide chains were identified to be proline and tyrosine, respectively. At pH 8.0 the Michaelis-Menten constant and maximum attainable velocity were found to be 8.1 muM and 27 muM Fru-1,6-P2 split/min per mg, respectively. The buffalo muscle aldolase was found to be similar to rabbit muscle aldolase in physico-chemical properties. However, the two enzymes differ significantly in pH optimum; the p optima of the buffalo and rabbit enzymes were determined under identical conditions to be 8.0 and 8.6, respectively.