STRUCTURE-FUNCTION-RELATIONSHIPS IN HUMAN RIBONUCLEASES - MAIN DISTINCTIVE FEATURES OF THE MAJOR RNASE TYPES

Human extracellular ribonucleases (RNase), together with other members of the mammalian RNase superfamily, can be classified into four diffe rent enzyme types on the basis of their structural, catalytic and/or b iological properties. Their occurrence and main distinctive features h ave been described, and catalytic differences (action on single- and d ouble-stranded RNAs, dependence of enzyme activity on pH, ionic streng th and cations, and hydrolysis of cyclic nucleotides) have been compar atively analyzed and discussed. In addition, some data considered here concerning human nonpancreatic-type RNases may support the suggestion [Chuchillo et al. (1993) FEBS Lett. 333, 207-210] that the enzyme 'ri bonuclease', presently classified as 'hydrolase', should be reclassifi ed as 'transferase'. (C) 1997 Federation of European Biochemical Socie ties.