Purification and characterization of three ribonucleases from human kidney: Comparison with urine ribonucleases

Structure–function relationships in human ribonucleases: main distinctive features of the major RNase types

“…Human ptRNase 1 shows indeed optimal activity with RNA as substrate at pH 8.0, and a hydrolytic activity towards 2',3'-cyclic nucleotides which is comparable to that of bovine RNase A [7,8,13,17,24]. Human nptRNase 2, shows its pH optimum shifted to lower pH values (6.5-7.0) with yeast RNA as substrate [17,24,28], and is unable to catalyze the hydrolysis of cyclic nucleotides at a measurable rate [12,17,20]; this is also true for nptRNase 3 [36].…”

“…However, it is now clear that these designations are not appropriate and might be confusing. Indeed, in some human 'nonsecretory' tissues (for example, brain [7] and kidney [8]) the only, or the major, expressed ribonuclease has been characterized as a 'secretory' RNase. In addition, it has been shown [9] that the human genomic DNA coding for eosinophil-derived neurotoxin (EDN), the so-called human 'nonsecretory' RNase [10][11][12], encodes a signal sequence typical of secreted proteins.…”

“…This enzyme [16] has been isolated mostly from pancreas [13], but enzymes which are products of the same gene (with different post-translational modifications) have also been purified from urine [24], seminal plasma [25], brain [7], and kidney [8]. In this enzyme, depending on the tissue origin, the glycosylation patterns of the three Asn-Xaa-Thr/Ser sites (Asn-34, Asn-76, Asn-88) are, indeed, quite different [16,26,27].…”

“…This enzyme [10,11] (also named EDN) occurs predominantly in spleen [28], eosinophils [29], liver [30], and placenta [31], but has been also isolated from urine [24], and kidney [8]; all these proteins (with quite similar glycosylation patterns [32]) are products of the same gene. In the sequence of this RNase, five amino acid positions (17, 59, 65, 84 and 92) with asparagine-linked carbohydrates have been identified [10] and their iV-glycan structure [32] is very different from that reported for ptRNase 1 [27].…”

Human extracellular ribonucleases: multiplicity, molecular diversity and catalytic properties of the major RNase types

“…This enzyme [16] has been isolated mostly from pancreas [15], but enzymes which are products of the same gene have also been purified from urine [32], seminal plasma [33], brain [34] and kidney [35]. In fact, only one gene coding for this RNase has been detected in human DNA by Southern blot analysis [36], and the amino acid sequence derived from the DNA sequence [37] was shown to be identical to the protein sequence [16].…”