MOLECULAR-PROPERTIES AND A NONIDENTICAL TRIMERIC STRUCTURE OF PURINE NUCLEOSIDE PHOSPHORYLASE FROM CHICKEN LIVER

Some molecular properties of crystalline purine nucleoside phosphorylase (purine nucleoside: orthophosphate ribosyltransferase, EC 2.4.2.1) from chicken liver were investigated and discussed. The MW of the native enzyme was 89,000 as determined by gel filtration and sedimentation coefficient, and 90,000 by sedimentation equilibrium. The enzyme was assumed to be a trimer consisting of 1 large subunit and 2 identical small subunits. The MW of 2 different sized subunits were 32,000 and 28,000 as determined by sodium dodecyl sulfate gel electrophoresis, and 30,000 and 27,000 by 6 M guanidine hydrochloride gel filtration. The amino acid composition was determined and the partial specific volume was estimated to be 0.735 ml/g.