title: Ribonuclease from cytosolic fraction of human erythrocytes.
abstract: Ribonuclease (RNase) activity is detectable in only one third of specimens of human erythrocyte haemolysates. On the other hand, treatment of erythrocytic cytosoles with sulphosalicylic acid reveals an inhibitor-bound RNase activity which is present in all erythrocyte specimens studied. The level of the erythrocyte inhibitor-bound RNase activity is comparable to that in human lymphocytes. Isolated RNase from the cytosolic fraction of human erythrocytes is poly-C avid RNase with maximum activity at pH 6.5. The enzyme is resistant to treatment with strong acids and heating up to 95 degrees C. Molecular filtration of the erythrocyte RNase shows that it is composed of two fractions differing in molecular mass, 19 000 and 15 000. No difference in enzymic properties between these fractions was found. The general properties of erythrocyte cytosolic RNase are much like those of acid RNases of human granulocytes and lymphocytes. As the erythrocytes do not metabolize RNA no function for the inhibitor-bound RNase can be suggested. Assuming that the observed erythrocyte RNase is the residual enzyme, persisting in the cell since it was functioning in the nucleated erythrocyte precursors, one may surmise that levels of free and inhibitor-bound erythrocyte RNase activity may be related to the normality or abnormality of erythrocyte maturation.
mesh_terms: D000293:Adolescent; D000328:Adult; D003600:Cytosol / Q000201:enzymology; D004905:Erythrocyte Aging; D004912:Erythrocytes / Q000201:enzymology*; D005260:Female; D006098:Granulocytes / Q000201:enzymology; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008214:Lymphocytes / Q000201:enzymology; D008297:Male; D008875:Middle Aged; D008970:Molecular Weight; D012260:Ribonucleases / Q000097:blood* / Q000302:isolation & purification
chemical_list: D012260:Ribonucleases